Home to 100,000 ... the tin roofs of the shacks of Klong Toey, Bangkok's shanty town. Credit:John Hulme The Barkers work for a Christian charity called Urban Neighbours of Hope, which they started in Melbourne in 1993. The idea is that they embed themselves in an area of need and help the locals, not by importing fancy programs and tonnes of money, but by simply being good neighbours. Today, for instance, Anji, who is trained as a social worker, is visiting one of her "patients", a man I'll call Leung, who lives by himself and is dying of AIDS and drug-resistant tuberculosis. Leung is not particularly popular in the slum, as he worked most of his life for a local gangster. According to Anji, most people are still a bit scared of him. "They say, 'Why do you help him? He's a bad person!' And I go, 'Yeah, but he's still a human being.' " We arrive at Leung's shack, where he's lying on a foam mattress on the floor. He has the body of a nine-year-old and the face of a mummy - sunken cheeks, sallow eyes and unusually dark skin. "That's what happens when they're dying," Anji tells me. "Their skin turns darker." Anjii sits and talks with him, asking him what he needs, when he last ate, if his legs ache: in the past she would massage his thighs which, due to lack of oxygen, are in an almost permanent state of cramp. Then she collects a big green oxygen bottle that she brought here a few days ago, so she can get it filled. "If you get really sick here," she says matter of factly, "it's best that you just die quickly, because no one else can afford to look after you. They're too busy trying to look after themselves." Klong Toey borders the Chao Phraya River, and is Bangkok's oldest and biggest slum. It was founded in the early 1950s by workers brought to the city by the government to help build the port. The workers, mainly from the poor rice farming area of Isaan in the north-east, erected their shanties beside the construction zone. While building continued, they had rental authority over the land. As soon as it finished, however, the government claimed all the land around the port, including the workers' homes. "One day they were legally renting," Ash says. "The next day they were squatters."

Anji Barker. Credit:Tim Elliott The lack of legal rights is one of the slum residents' biggest problems, along with overcrowding, bad sanitation, poor access to health care, endemic crime, drug dealing and an absence of legitimate jobs. In 2003, the government tried to ease the overcrowding by building high-rises in an area of the slum called Rom Kloaw, but that didn't really work, partly because the chosen site was an old pig slaughterhouse, which spooked the locals. "Also, in a flat area, you can sell things out the front of your house, something you can't do in a high-rise," Ash says. As more people flocked to Klong Toey - 20,000 in the past 10 years - the slum has grown, higgledy-piggledy, like a giant cubby house, with bits of timber and iron tacked on to other bits of timber and iron. Seen from above it resembles a warped quilt of rusty sheeting held down with rocks and cloth and bits of lumber. In the dry season, the slum is merely uncomfortably hot; in summer it is sweltering, the breathless alleys dripping with humidity, the garbage dumps boiling with bacterial ferment. In the Barkers' house, a boxy two-story structure they rent from a local gangster, the plywood walls of their bedroom become too hot to touch. "Sometimes you can't move," Anji says. A street kid in Lok 1, one of the most dangerous areas of the slum. Credit:Tim Elliott Asked how they ended up here, Ash likes to say "We were called." But it's more complex than that. "I'd always grown up being taught that the best way to serve God was to help those who most needed it," he says.

In 1990, he began working for Youth For Christ in Melbourne, helping refugees and heroin addicts and making prison visits. "It struck me that the guys we saw in prison only came from certain neighbourhoods - Footscray, Springvale, Heidelberg, Dandenong. Definitely not Toorak." Former prostitute Lek in her home in Klong Toey slum. Credit:Tim Elliott Ash and Anji, who had married in 1989, started up sports clubs and camping trips for these people. "But it wasn't enough to do one or two days a week. It was their whole lives that made them vulnerable." In 1993 they launched Urban Neighbours of Hope (UNOH). Its mission: to "embed" volunteers in disadvantaged communities, where they would harness "the gifts of the locals" to initiate change from the ground up. Having started in Springvale, the group now has eight teams operating in Sydney, Melbourne, Auckland and Bangkok. UNOH workers take what amounts to a vow of poverty, surviving on an income from the organisation that is capped at the local poverty line, the idea being that they can better identify with their neighbours' circumstances. (The Barkers "cheat" a bit in Bangkok, giving themselves about $2000 a month for a family of five.) The narrow streets are crowded with people and goods. Credit:Tim Elliott

"Lowering our income frees us up," Ash says. "Money can be great, but it can also be a distraction; it tempts you to spread yourself thin, whereas our model is all about focusing deeply." In the late 1990s the Barkers looked into expanding UNOH overseas. They visited Vietnam, but eventually settled on the Klong Toey slum, where they spent a three-month sabbatical. In 2000, they decided to relocate and gave themselves 18 months to get organised. They sold or gave away most of their possessions, took a crash course in Thai and established contacts in the slum. "You can't just rock up," Ash says. "The days of Christians just turning up uninvited are long gone, thankfully." The first six months in Klong Toey "were hell," Ash says. "Just learning the language was so hard. There are 44 consonants, 32 vowels, five tones. The word 'ma' has five different meanings depending on the tone." Then came illness. Within the first year or so Ash had contracted dysentery, typhoid, typhus and all four strains of dengue fever. "Haemorrhagic dengue was the worst. I honestly thought I was dying. I remember the doctor coming into hospital and telling me that my platelets were in free fall and that if they didn't stop I could start bleeding from my ears, eyes and nose and then die. And then he smiled. They all smile here." Life in the slum initially seemed chaotic. But slowly codes of behaviour became apparent. Parts of the slum were run by different gangs. The gangs are connected to the police who give them permission to do what they do, whether it be dealing yaba (a type of speed) or ice, or operating gambling dens or loan sharking (going interest rate: 30 per cent). The Barkers got to know the locals - the gang matriarch they call "Screaming Lady", who walks through the slum yelling at everyone; the alcoholic who died on their doorstep; the glue sniffing woman who went crazy and had to be chained to the fridge in her house to stop her walking around naked; and someone they call "Poo Man".

"Poo Man was a neighbour who had diabetes," Anji says. "One day he went into diabetic shock, got brain damage and lost all impulse control. So he would crap everywhere and wipe it all over himself, in his eyebrows, all over his home, where he lived with his sister. He'd walk into our place, trailing poo everywhere and open our fridge and eat tubs of margarine." Anji would visit Poo Man regularly; clean him up, trim his eyebrows, give him insulin injections and Imodium to block him up. "He finally died, just recently, which was a blessing, really." Apart from just being there for people, the Barkers started simple projects: a soccer club, a kindergarten, English classes; they raised money to rebuild the local school, which was made of sticks and asbestos. ("You'd arrive in the morning and there'd be asbestos dust on all the books," Anji says.) They organised dental care for the children and improved their diet; if the kids had parents in jail, Anji would take them on day visits. The Barkers had their own children - Amy, who was five when they moved into the slum, and Aiden, who was born in 2003. (Both Amy and Aiden went to an international school, outside Klong Toey. "This was important," Ash says. 'We didn't want them to suffer because of our choices.") Ash and Anji have also taken in two foster children, little boys, Tan and Film (pronounced "Fim"). Film had been abandoned by his mother, a prostitute, when she went to work on the floating brothels that service ships off Malaysia. Film is blind in the right eye - his mother had an STD when she gave birth to him - and is partly deaf. He also has "cognitive deficits" from his mother's drug use during pregnancy. Not that any of this has earned him special treatment. When I ask Aiden how he regards Film, he says: "Like a brother. He's blind in one eye, so it's really easy to sneak up and scare him." One of the first people the Barkers met in Klong Toey was a woman called Lek. "She was a lifesaver," Ash says. "She helped us with everything."

One day, Ash introduces me to Lek, who is 47 and lives by herself in the slum. Lek was born in the south of Thailand, but moved to Bangkok when she was eight. She is one of 16 children. Soon after the family arrived, their house burned down and her father left. Instead of going to school, Lek worked in a squid factory. At 17, she was married to a 50-year-old man as his third wife (polygamy is common in Thailand), but the man abused her, so she left to live with her sister. With no money, Lek agreed to be trafficked to Hong Kong, where she worked as a prostitute. "My mother didn't like me doing it, but I was supporting my family," she says. In Hong Kong she was locked in a cupboard and only let out to work, servicing up to 20 men a day. With the help of a client she escaped, but was caught and locked up by the police who raped and beat her. (The abuse rendered her unable to have children.) She returned to Bangkok at the age of 23, only to discover her mother had became heavily indebted to loan sharks. She again agreed to be trafficked, this time to Singapore. Eventually she married one of her clients, a Singaporean man, but he couldn't keep her so she spent most of her time in Bangkok. "By the time we met Lek she was still a working girl," says Ash. "The older she got, the more dangerous the clients she'd be forced to take." Determined to get her out, Anji set Lek up in Klong Toey Handicrafts, a fair trade initiative the Barkers established with women from the slum. Lek was good with her hands and hard work didn't bother her. Klong Toey Handicrafts now turns over $200,000 a year, and employs scores of people. Lek, the project's co-ordinator in Thailand, often visits Australia to oversee sales networks, and in the course of her travels has developed an abiding love of, of all things, pavlova. As a social worker, anji avoids making judg- ments, not only because it's not her job to judge but because she realises that she "might not actually understand" what she sees. That said, there are some aspects to life in the slum that she has struggled to accept, "and the child sex culture is one of them". By Western standards, Thailand is highly promiscuous: sex is commonly regarded as just another type of manual labour. In addition to that, Anji says, "the boundaries are very blurred. I know families whose mums allow their husbands to have sex with their daughters. I have done pregnancy tests for 17-year-old girls who are pregnant to their dads, to their granddads." This has presented some interesting theological conundrums. "There's one guy we know, who is married to one of our workers, who is particularly bad," Anji says. "He's impregnated his daughter, he steals from his wife, he's constantly on drugs and sleeping with different neighbours." He was such chaos that Anji and some of her staff had a debate as to whether it was okay to pray that he died. "Some of the staff reckoned it was not okay, but I decided it was," she says.

Life for the Barkers' eldest child, Amy, was no less challenging. At the international school she spent the day with the children of Thailand's elite: generals, embassy people, expats. "I'd go to parties in these enormous mansions and then Dad would come and pick me up on his scooter and we'd go back to our wooden shack," she laughs. She loved it, she says. "It gave me a lot of perspective on things that I wouldn't have had." And yet she was living in "two different worlds. There were my rich friends from school and then there were my slum friends, who if they were girls were sent off on ships as they got older, or to brothels, or had gotten pregnant. There was such a large divide between the two groups, it was hard to know where I fitted in." Amy returned to Melbourne in 2012 to complete her schooling. With her gone, the Barkers decided to move on, not just from the slum, but from UNOH itself, which they resigned from in October. "We've been at the head of it for 20 years," Ash says. "By leaving now we allow the next level of leadership to come through." To make sure that they don't tread on anyone's toes in Australia, they are moving to "a lovely housing estate" in Birmingham, UK, next year to start what they hope will be a sister organisation to UNOH. They hope to work closely with the Bangladeshi community there. There won't be any pythons, and the weather will be decidedly cooler, but the issues of need will doubtless remain the same. "Look at this," says Ash, showing me a photo of the street they are thinking of moving to. It's a row of tenements: cold, drab, utterly dismal. "Looks beautiful, don't you think?" he says.