Bangkok: As the iron-plated gate is bolted drearily shut behind the petite blond visitor entering the courtyard of the notorious "Bangkok Hilton" prison, a dour guard turns away from inmates shuffling by in heavy leg irons.

"Susan!" he hollers, suddenly sunny, waving at the woman. "You look beautiful today!"

She laughs and teases back in fluent Thai: "Only today?"

For over a decade, Susan Aldous has been coming to Bang Kwang, as the maximum security prison is officially known, several days a week to make good a promise to herself "to turn this place around by getting a smile out of every guard and prisoner".

"It's working, you see!" she beams.

For two decades, the unaffiliated, unpaid volunteer has also been a constant presence at Bangkok women's shelters, hospital wards, slums, and upcountry orphanages, tending to the needy, the abandoned, and the despondent.

"Susan is making life bearable and worth living," says Jaganathan Samynathan from behind a double row of iron bars in the visitors' section. A Malaysian of Tamil ancestry, he was sentenced to death in 1992 at age 24 for attempted drug trafficking but was given reprieve in the form of a life sentence. No one but Aldous has ever visited him in the jail.

Single mother

Aldous lobbies friends and acquaintances for small donations for hard-up inmates, appears in court on their behalf for royal amnesties, and pops up in holding cells to counsel detainees and in police rehabilitation facilities to nurse junkies. She's laid on feasts for prisoners, got guards new walkie-talkies, and obtained medicine and equipment for the prison hospital.

"In between," Aldous says, "I try to do my laundry and brush my teeth." She's a single mother with no income other than small donations from strangers, friends, and the relatives of prisoners to pay for her $120-a-month (Dh440.7) apartment that she shares with her 17-year-old daughter. A youthful sprite of a woman, Aldous wears only hand-me-downs and cheap backpacker-style trinkets. She eats curbside meals and walks a lot to save on bus fare. Her neighbours often slip money in envelopes under her door.

Her goodwill has earned her the epithet "Angel of Bang Kwang".

Aldous loves to kiss and hug. Everyone: HIV patients, abandoned women, world-weary transvestites, even a journalist she's just met. She creates camaraderie wherever she goes with her roaring laughter.

It's Saturday afternoon, and she's just arriving for her weekly rounds of a women's shelter. Aldous waves to a clutch of women - battered wives, rape victims, single mothers - unwinding in the leafy yard. "You're sitting there like in an old folk's home!"

The women cackle.

Children mob her. Aldous hands them toys and chocolates - two each so they can donate one to a sibling or friend. "This way they learn they never lose by giving - if only a smile, a kind word, or a helping hand," she explains.

Once, Aldous herself might have been a resident here. Raised by foster parents in an upper-middle-class enclave of Melbourne, she describes herself in childhood as a menace, "jamming pins into kids' butts" and terrorising classmates. By her teens, in the 1970s, she'd dropped out of school and was, by turns, a spaced-out flower child (like "Mary Poppins on crack," she says); a hell-raising skinhead biker in military fatigues; and a protopunk with tattoos, safety-pin piercings and shaved eyebrows.

Not yet 17, she was nicknamed "Petrol Head" for her gas, glue, and aerosol sniffing habits. She'd throw tantrums and slash herself with razor blades, she says. "I was angry at the world and rebelled at a predictable life in the suburbs."

Wandering around Melbourne's red-light district, she encountered volunteers of a nondenominational Christian group. Aldous talked to them of suicide, when one of them suggested: "If you're going to throw your life away, why don't you instead give it away?"

Compassion has been "my drug of choice" ever since, she says.

Aldous's close friend, Chavoret Jaruboon, is a soft-spoken, courteous man, and her most unlikely ally. Until the introduction of lethal injection recently, it was this senior guard's job to execute condemned prisoners in Bang Kwang - with a submachine gun. He's helped her with projects aimed to improve the lot of the neediest inmates. "Prisoners call us 'the Angel and the Devil'," he notes drolly.

"Thai people believe in karmic destiny," Chavoret says. "They say when you visit a prison you should walk in backward [so bad karma stays behind you]. Susan doesn't [believe that]."