But take a look at her now. A fetching young woman with a toothy smile and playful wit, Ang Srey Mom wears designer jeans with a cerise blouse sporting the logo "Fashion to reign on freedom"; she wouldn't look out of place among the trendy teens on Dundas Street, in Mong Kok. A budding fashion designer, she participated in the BBC's "100 Women" rights conference last October in London, sharing her story with British radio listeners. This year, Ang Srey Mom graduated from vocational school and had her first fashion show, at a garment factory in Dhaka, Bangladesh, at the invitation of textile magnate Rubana Huq.

"Once I had no hope, but now I am excited about the future. I have a dream," says Ang Srey Mom, in English, a language she now speaks fluently. That future includes an invitation to study clothing design on an internship in Hong Kong.

"[Ang Srey Mom] is an incredibly warm, vibrant and articulate young person who mentioned that her ambition is to become a designer in the fashion industry," says Aidan O'Meara, president of VF Corporation's Asia-Pacific operations. "It was clear she also had a sense of style.

"Our Lee Jeans brand designs a large portion of our regional line in Hong Kong so we think we would assign her to that team. The details of the internship need to be worked out but it would normally be about three months in duration and she would … [gain] practical experience in all facets of product design and development together with some exposure to the sales and retail functions.

"Having her work with us would also benefit [our staff in Hong Kong] as her story of triumph over adversity is one we can all learn from."

However, "it's because of Papa Scott" that she has come so far, acknowledges the young woman herself.

"Papa Scott" is Scott Neeson, a 55-year-old Australian who underwent a remarkable transformation of his own: from high-powered Hollywood mogul to committed philanthropist.

As head of 20th Century Fox International, Neeson helped ensure the global box-office successes of blockbusters such as , , and the Star Wars prequels. He lived in Beverly Hills, boasted a US$1 million salary, drove a Porsche, owned a yacht, dated supermodels and hobnobbed with the stars. Today, he gets around in a pick-up truck, sleeps in the nondescript office building of his Cambodian Children's Fund (CCF), on a narrow, potholed Phnom Penh street near the slums of Stung Meanchey, and spends all his time overseeing the work of a large-scale, relentlessly expanding charity that looks after some 2,000 severely disadvantaged children - aged between five weeks and 23 years old - and members of their families. Neeson professes to know every single one of CCF's young proteges by name.

His charity maintains five residential homes for hundreds of deprived youngsters, runs day-care centres and nurseries for toddlers in the rubbish pickers' shanty towns and operates satellite schools for children in the slums. It pays for education at government schools and organises sightseeing trips and sports days. It feeds more than 1,000 children each day and runs vocational programmes in garment design, tailoring, administrative skills, hair dressing and cooking, for older students.

CCF also organises leadership programmes to teach the poorest of the poor self-esteem and coach them in life skills, social responsibility, community outreach, human-rights issues and advocacy work. It distributes bags of rice and bottles of fresh water to squatters, schools them in hygiene and provides health and dental care for all the children, as well as for their siblings, parents and grandparents.

"I drive the staff crazy," concedes Neeson, whose charity employs some 400, most of them Cambodians and many of them former scavengers. "If I come up with a plan, I want to see it implemented within 48 hours. If I see a need, I want to do something about it immediately. You don't want to see suffering prolonged."

And he sees plenty of suffering. Bedevilled by the decades-long legacy of Pol Pot's "killing fields" and a subsequent civil war, millions of Cambodians continue to live in abject poverty in one of Southeast Asia's poorest countries, where corruption and human-rights abuses are rife. Scores of children are chronically malnourished and many of them never finish primary school. Their career prospects tend to be grim: dismally paid menial work, odd jobs as domestic helpers or employment in the country's underground sex trade.

"We want all of [CCF's children] to go on to higher education," says Neeson. "Forty children from the garbage dump have just started university. Hope makes a big difference. And the successes of some kids motivate the others. A 14-year-old girl I took off the garbage dump in 2006 is now studying to be a doctor."

She now teaches leadership classes as well, at a women's centre near the dump.

Neeson has seen the transformative virtues of self-belief, ambition and hard work in his own life. Born in Scotland, he moved to Australia at the age of five with his parents and older brother, later dropped out of high school and began working at rustic drive-in theatres in and around his hometown of Adelaide, busying himself in the marketing department by night and making doughnuts by day.

By the mid-1980s, the one-time school dropout had become a senior manager at Hoyts, Australia's leading cinema operator, first as head of programming then as managing director in charge of theatrical releases. By 1993, Neeson was in Hollywood, working for 20th Century Fox in Los Angeles as head of international marketing. Seven years later he was appointed president of the studio's international arm, overseeing a series of global blockbusters.

In 2003, he left Fox to head Sony Pictures' marketing operations but that same year, while on holiday in the Cambodian capital, he came face to face with poverty the likes of which he had never seen.

He set up an incipient charity to help some of the poorest children and thought that would be that. Then, a year or so later, during a return visit, the Hollywood executive found himself standing ankle-deep in rubbish at Stung Meanchey's sprawling landfill. Before him, in a haze of toxic fumes and burning waste, were swarms of destitute children rooting through the filth; they were jostling for scraps of recyclables in newly dumped loads, risking life and limb around smoke-belching rubbish trucks.

His mobile phone rang. Calling him from an airport back in the United States was a Hollywood superstar's agent, who was complaining about the in-flight entertainment on a private jet that Sony Pictures had provided for his client. He overheard the actor bellyaching in the background. "'My life wasn't meant to be this difficult.' Those were his exact words," he recalls.

"I was standing there in that humid, stinking garbage dump with children covered in sores and sick with typhoid, and this guy was refusing to get on a Gulfstream IV because he couldn't find a specific item on board," he remembers.

Citing another example of a fussy movie star he had to deal with, he says, "An actress wouldn't get on a private jet unless she knew the thread count on the seats. They had to be covered in Egyptian cotton with [an extra-luxurious] count of 800. She has people fly ahead of her to five-star hotels whenever she travels, to change the sheets in her suite.

"Here [in Phnom Penh], for US$80 a month, I had two children going to school and their families lived in nicer rooms. I didn't give much to charity before. I had the usual excuses: 'It's not my problem.' But standing there on the garbage dump, I realised it was my problem and could not, in good conscience, walk away."

Within months Neeson had quit Hollywood. He sold his mansion and held a garage sale for "all the useless stuff I owned", his yacht included. His sole focus would now be his newly launched charity.

"My life in Hollywood was good. I had a nice house, I knew the stars, I loved my dogs," says Neeson, an affable man with prematurely ageing features and a ready, high-voltage grin. "But it's the difference between going to Disneyland and wanting to live there. You've only got one life. It'd have been a terrible waste to [work in Hollywood] for another 10 years."

His decision shocked everyone who knew him, including members of his family.

"Scott always wanted to push the boundaries," says Neeson's brother, Norman, a film producer in Australia, during a visit to Phnom Penh. "We advised him against going to Hollywood and we advised him against leaving it. Scott didn't listen and it's good he didn't. Once you see the children, their needs and their gratitude, you understand why he's done what he's done."

Neeson has burned through his savings, pouring them into his humanitarian projects, the costs of which now amount to US$5.5 million annually. You might think his old friends and colleagues in Hollywood would be flocking to help underwrite some of his projects, but you would be wrong.

"People in Hollywood have very short memories," he observes wryly.

Not all of them do, however. Viacom owner Sumner Redstone, act-ress Heather Graham and German-born director Roland Emmerich (, and ) are among CCF's backers, having raised or donated millions of dollars over the years for Neeson's humanitarian projects.

American skateboarding legend Tony "The Birdman" Hawk, who recently visited Cambodia on a publicity tour, is among the celebrities who sponsor individual children, paying for their studies and other expenses to the tune of US$100 a month. Individual sponsors also include several Hongkongers and, at a recent fundraiser in the city's Renaissance Harbour View Hotel, US$600,000 was raised for the Cambodian charity, with General Electric Hong Kong, Credit Suisse and Hong Kong Broadband Network being the major donors. Ang Srey Mom was among the handful of CCF proteges who travelled to the event to speak about their experiences and about the charity's work.

Neeson, with a can-do spirit and an eye for detail honed by 25 years in the movie business, takes a very hands-on approach to charity. Every day, at dusk, as the scavengers begin returning to their modest homes after another day at the dump, he sets out on his "Pied Piper routine", as his brother calls it. With a helper or two in tow, Neeson pays house calls on his proteges, navigating the filthy pathways that meander among scabrous clusters of shacks, fetid puddles and noxious heaps of rotting rubbish.

Everywhere he goes children emerge from shacks and hovels, racing up to him with cries of "Papa! Papa!" They leap into his arms, tug at his shirt, cling to his limbs, wrap themselves around his legs.

When Neeson spots certain children, he hands them portraits of themselves from a sheaf of newly printed A4-size photographs.

"I want them to have mementoes of themselves when they grow up and leave all this behind," explains the Australian, an avid photographer who painstakingly documents each child's "before" and "after" transformation, from scruffy, sickly ragamuffin to ruddy-cheeked, well-groomed youngster in spotless school uniform. In return, they give their benefactor drawings.

On the outskirts of a squatters' village Neeson stops at a newly renovated two-storey townhouse with tall protective walls, behind which workers are laying concrete in the front yard. It's a rented building the philanthropist has turned into a shelter for young victims of sexual abuse and domestic violence, both of which are rampant in the slums. The girls within are clothed, fed, housed and schooled; they also receive counselling from professionals.

"We have a new case a day," Neeson notes sombrely. "This girl here," he says, indicating a shy and petite eight-year-old in a light-blue dress with teddy bear prints, "she was raped by an uncle."

He indicates another girl, a 10-year-old in a crisp new student's uniform who has just returned from a nearby government school: "Her mother tried to kill her twice. Took a knife to her, then tried to drown her. [The mother] told me, 'If you care about her so much, you take her.'"

A tiny seven-year-old with pigtails tears herself away from a gaggle of friends who are merrily scooping out the last dregs of ice cream from a tub and runs up to him. Neeson scoops her up in his arms.

"Come on, Lily! Beautiful button, isn't she?" he coos. "She's smart as a whip. Her father beat her mother to death and buried her in the back."

Many slum residents are migrants from the countryside who have fallen on hard times after driving themselves into debt. Some took to the bottle, others gambled their families' meagre savings away, yet others could not repay the 10 per cent interest on simple loans borrowed from local lenders. With no employable skills, they've wound up at the dump, where their lot has gone from bad to worse. Alcoholism is endemic, especially among the men, and so is violence.

Foreign paedophiles, too, come prowling for young victims, posing as kind benefactors and blatantly offering to buy children from their parents. In 2010, Neeson helped expose a 62-year-old British man who had served time in his homeland for the statutory rape of a 16-year-old and was grooming children at the dump by buying them toys and snacks. The retired hairdresser offered £150 (HK$1,940) to an impoverished mother for her 17-year-old daughter, saying he was planning to "adopt" the teenager. When Neeson learned of the offer, he rushed to negotiate with the woman, offering to pay off her debts in a bid to rescue the girl. CCF also notified the authorities. Facing charges of child abuse, the man fled Cambodia and was later arrested in Bangkok, Thailand, on charges of raping a girl in Stung Meanchey.

"People like him are a constant source of worry for us," Neeson notes. "Some parents at the dump will gladly sell their children."

To help break the cycle of financial dependency that fuels slum dwellers' poverty and antisocial ways, Neeson's charity runs a micro-lending scheme.

"We finance their bad loans and the family pays us back when they can," he says. "A family here makes around US$2.50 a day and, if they have to pay US$1.50 in interest on a US$300 loan they took out, they'll never get out of penury."

Neeson cites a recent success story: "One father did misbehave badly, was occasionally violent. We gave him a small loan, he bought back his small plot of land [in the countryside] and started growing watermelons. Then, one day, he showed up with a load of melons for us [out of gratitude]."

Small sums can make a big difference. Choun Theary, a dump scavenger originally from the neighbouring province of Prey Veng, has received a US$60 loan from CCF. The woman used the money to set up a mobile hair-cutting and nail-polishing business, which helps her earn US$5 a day.

"My husband drank a lot and left me with the children," says the mother of five, who looks at least a decade older than her 43 years. For two decades she lived at the dump but recently she has been rehoused in one of the modest but comfortable homes CCF has been building for single mothers and their children both in the shanty town and outside it.

"I never thought I'd be so lucky," she says. "Without help from CCF, I would still be living at the dump. But now my children go to school. They will have a much better life than I've had."

"I was surprised to see kids get three meals a day and have tuk-tuks take them from the dump to school and back," says Chek Sarath, a Cambodian man who grew up hungry and neglected in a state-run orphanage but now works for CCF as a driver. "Mr Scott places the children's well-being above his own."

A few months ago, Neeson came down with dengue fever. Soon afterwards he needed to be hospitalised with a bacterial infection. But he ploughs on.

During one of his evening sojourns, Neeson visits the shanty town's oldest resident. In Soy is a diminutive 103-year-old grandmother, now shrunken and bald but still lucid and proud, who survived a century of bloodshed and political turmoil only to wind up in her twilight years in a rickety wooden shack at the Stung Meanchey dump. She is looked after in CCF's "granny programme", receiving food and health care.

"My fear is that once this generation passes, old Cambodian values will forever disappear," Neeson says, explaining why CCF records the life stories of the elderly in its care. "They're the backbone of this society and the children have much to learn from them."

Nearby lives Yos Sam Onn, who survived the killing fields - which claimed the lives of some 1.7 million Cambodians in systematic genocide carried out by home-grown Maoist guerrillas between 1975 and 1979 - while working at a commune in Prey Veng.

"I used to have madness because I'd lost everything: my mother, my home, my siblings, my farm," the elderly woman told CCF's interviewers. "My mother died. My father and my brother were killed. Even my brother's children were killed and buried in a hole.

"But now my mind is pure. I never think about those terrible things any more. Because of Mr Scott, I feel like the sun is shining on me again. Now I am finally at peace and hopeful in my final years."

Neeson carries on with his walkabout, heading down a winding path flanked, on one side, by a slapdash row of rickety shacks outside which bare-chested men sit and drink, and, on the other, by a rubbish-strewn, putrid wet patch in which scrawny chickens root around for food. He takes a right turn down a dark narrow alley, tiptoeing around an ankle-deep puddle of fetid rain water. "There's a little bit of drug use here by the locals, so be careful," he calls out.

His destination is a small cinderblock home with no windows and cramped, gloomy interiors illuminated - barely - by a single bulb. A family of eight, including a newborn, sleep here at night on a single, well-worn futon and bedspreads laid on the floor. In pride of place on a wall is a large photo, courtesy of Neeson, of a smiling girl holding a certificate from one of CCF's satellite schools, where the children of scavengers learn English and computer skills. Next to it hangs the diploma itself, proclaiming 12-year-old Neth Soklin "Best Newcomer, 2012". Another framed award declares the girl to be "Most Improved Student, 2013".

CCF hands out such awards regularly to keep students motivated. By studying hard, they can also earn food vouchers and bags of rice for their families.

"Children had to feed their families by working at the dumps; now they can feed their families by being good students," says Mao Saret, 25, who works in community outreach for CCF.

Neeson moves on. Up ahead, in the gathering dark, a woman wails inconsolably in the centre of a small gathering inside a wooden hut, where a body wrapped in white shrouds lies among flickering candles. Her 16-year-old daughter died in a motorcycle accident.

"She's not one of ours," Neeson notes, after making some inquiries about the teenage girl. "We have to make sure the family gets financial help for the funeral," he tells a Cambodian aide.

As he continues, Neeson reels off details about some of the onlookers: "This girl has an abusive father. That guy got shot. That one there lost an arm in an accident."

He runs into Srey Ka, a pretty 13-year-old with a coquettish smile and large patches of knotted scars on her upper body - the legacy of having fallen into a fire while sorting rubbish when she was six. Now she speaks fluent English, is studying hard and wants to be a doctor. Recently, she accompanied Neeson, with several other children, on a trip to Hollywood.

"That's Lyn." Neeson points at a timid little girl with a head newly shaven, to help treat scabies and lice. "I just found her on the dump."

"There's my favourite girl!" Neeson exclaims, tussling the hair of Net, a smiley seven-year-old who has moseyed up to him. "No parents. Lived on the dump. And always so happy."

Then, torch in hand, on he moves and, after heading down another mucky path, points to a sizeable plot of marshy swamp with only a couple of tumbledown shacks standing on it.

"This will be our new Institution of Educational Excellence," he proclaims.

Right here, in the heart of the slum, will rise a four-storey building that will have well-appointed classrooms staffed by qualified teachers. In charge of the school will be Kevin Tutt, former principal of Prince Alfred College, in Adelaide, one of Australia's most prestigious private schools.

"We'll offer world-class standards of education, the best we can do for these kids," Tutt promises. "We'll need to think big."

Tutt, 57, recently decided to leave the 145-year-old Adelaide institution and relocate to Phnom Penh, to head CCF's educational programme.

"It's certainly going to be a different environment," he concedes, while accompanying Neeson on tonight's round. "All this poverty gets under your skin, but look at these kids. The greatest gift we can give them is education. I loved my job in Australia, but here you can make a real difference and witness the transformative power of education up close."

And witness it you certainly can.

Nearby, behind a high-security fence, is one of CCF's satellite schools. Inside, sitting in neat rows in brightly painted classrooms decorated with the images of cartoon characters, children learn English and maths in evening classes. On a wall, written in a child's hand, are large words in red: "We can because We believe." Where the school now stands there was, until recently, a huge mound of rubbish.

"For a variety of reasons some children couldn't attend regular school so we've brought the school to them," Neeson says. "Now the vast majority of our students live within a five-minute walk of one of these schools."

In an alcove at the back he spots a group of young children, their eyes glued to a Disney cartoon playing on a television set.

"I miss a lot about Hollywood," Neeson admits. "I miss Sundays play-ing paddle tennis on the beach with friends and taking the boat out to the islands."

As he hands a box of coloured pencils to a little girl, who squeals with delight at the gift and thanks him by pressing her palms together respectfully in a Khmer-style greeting, the Australian smiles and adds: "One of the greatest joys is to be part of these children's lives, seeing the glow in their eyes when they start to realise that the world can be a pretty wonderful place after all."