The quirky, energetic campaigner boasts a string of celebrity supporters and has been named a CNN hero of the year, but she is as divisive among anti-trafficking activists as she is beloved by the international press.
Most recently, Mam kicked up a storm of controversy when she allowed her old friend, New York Times correspondent Nicholas Kristof, to live-tweet a brothel raid in the northern Cambodian town of Anlong Veng in November.
"Girls are rescued, but still very scared. Youngest looks about 13, trafficked from Vietnam," Kristof wrote to his more than one million followers on the Twitter microblogging website, in remarks that trafficking experts say raised questions of safety and consent.
For Mam, who created the anti-trafficking organisation AFESIP and now runs an eponymous foundation, the benefit of the attention Kristof brings to trafficking issues outweighs the security concerns.
"Even if you're not tweeting it is also dangerous... but if (Kristof) tweets it, it's better because more people get awareness and understanding," Mam told AFP in an interview during a visit to Vietnam.
Tania DoCarmo of Chab Dai, an anti-trafficking group working in Cambodia, said the raid coverage was an unethical PR stunt which broke Cambodian anti-trafficking laws and which sensationalises a very complex issue.
"Doing 'impromptu' coverage of children in highly traumatising situations would not be considered ethical or acceptable in the West...it is inappropriate and even voyeuristic to do this in developing nations such as Cambodia."
"This is especially true with children and youth who are unable to provide legal consent anyway," she said.
AFESIP says it has been involved in rescuing about 7,000 women and girls in Cambodia, Thailand, Laos and Vietnam since 1997.
In Cambodia alone, there are more than 34,000 commercial sex workers, according to a 2009 government estimate.
The line between victim and trafficker is often not always clear. Women who were tricked into working in a brothel may go on to recruit others in the same way.
Mam, who is in her early-40s but does not know her exact year of birth, was sold into a brothel in her early teens by a man who she says was either her grandfather or an uncle and then repeatedly raped and abused until, after watching a friend be killed in front of her, she managed to escape.
"I was completely broken," she said, adding that this experience of being a victim is something she cannot forget and is what drives her anti-trafficking campaigning.
Within the anti-trafficking field, Mam takes a controversially hardline stance: all sex workers are victims, whether of trafficking or circumstance, as no woman would really choose to work in a brothel.
"Sometimes a woman -- she tells me she is choosing to be a prostitute (but if you ask) how about your daughter? You want her to be? She'll say: No, no, no'," said Mam. "(They) have no choice".
This position, which underpins Mam's reliance on brothel raids as a tool to fight trafficking, enrages other activists, such as the Asia Pacific Sex Worker Network, which argues consenting adult sex workers need rights not rescues.
Sweeping raid-and-rescue operations and police round-ups of street-based sex workers are not only ineffective, experts say, but lead to systematic violations of sex workers' human rights, New York-based Human Rights Watch said in 2010 report.
Mam's organisation, AFESIP, has also been criticised for accepting sex workers picked up during Cambodian police round ups which HRW has said constitute arbitrary arrests and detentions of innocent people.
Mam dismissed HRW's assessment.
"When a girl has been killed in the brothel does HRW go into the brothel? So who are you exactly? When I am in the brothel, one of my friends was killed. Did HRW go there? No," she said.
Consenting, adult sex workers detained during the police raids -- who say they were neither victims of trafficking nor wanting AFESIP's services -- have also reported being held against their will at AFESIP shelters.
"The first time (a sex worker) come to the shelter she don't want to stay ... because she don't know us," Mam said, adding that women are so broken by sex work they want to stay in the familiar surroundings of the brothel.
"I always say: please, can you just stay one or two days, treat it like a holiday," she said, adding that if women chose to stay in the brothels she respected that decision.
"I'm not going to force them, I have been forced my own life. It's up to them," she said, adding that this applied within the shelters, with no girl being forced to speak to the press or share her experiences with anyone.
Mam says she tries to listen to and learn from criticism of her tactics and approach, adding that she has "made a lot of mistakes in my life," and has never claimed to have all the answers to how to end sex slavery.
"What I know how to do is just helping the women," she said.