Siem Reap, Cambodia - Using tip-offs, stakeouts and stealth, civilian investigators are playing a crucial role in helping Cambodian police track down foreign paedophiles, as they battle to spread the message that the impoverished nation will no longer be a playground for abusers.
Down a dark side-street off Siem Reap's boisterous red light district, a Cambodian man sits in the driving seat of an auto-rickshaw, a cigarette hanging from his lips, his eyes fixed on a bar across the road.
But he is not touting for passengers. He is an undercover informant on a stakeout, a concealed notepad and camera the only giveaway of his trade.
His target for the night is a Western man who has raised suspicions because of his behaviour with children, triggering an around-the-clock surveillance operation.
"When there is a suspect, we send our agents down to look at the area, keep an eye out for movement and suspicious activity," Meas, a 38-year-old investigator who runs a network of civilian informants in the central Cambodian city, told AFP.
Southeast Asia has long been a global epicentre for child sex abuse by both Western and regional tourists.
A landmark study released Thursday by a coalition of nearly 70 child protection agencies looking at child sex abuse by tourists around the world says that while some successes have been made in Southeast Asia, it remains an "enduring phenomenon that has plagued the region for several decades".
Cambodia has transformed itself from a war ravaged nation into one of Asia's fastest growing economies and an increasingly popular tourist destination.
But it remains poor and has an unenviable reputation as a sex tourism hotspot, including for paedophiles drawn to a country where children can still be bought and all too often, police also have a price.
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Cambodia's grim reputation as a child sex hub caught global attention when British glam rocker and serial paedophile Gary Glitter was eventually deported in 2002 after years living in the region in impunity.
Enforcement has significantly improved since then, but there are still wide gaps in the safety net and civilians supplement the policing.
Meas, who asked AFP to use a pseudonym, is an investigator with Action Pour Les Enfants (APLE), a charity which specialises in catching paedophiles and caring for their victims.
The year after Glitter was deported, there were just eight paedophile arrests according to government data, but no recent detailed figures have been released.
Last year, APLE's own investigation led to 22 arrests and the charity says perpetrators and accomplices tend to be evenly split between locals and foreigners.
Meas said he has personally overseen investigations that have busted around 60 people. But investigators know they cannot rest on their laurels.
"While the situation in Cambodia is getting better each year, the fight is not nearly over," Khoem Vando, APLE's deputy director of field operations, told AFP.
"Foreign paedophiles are still targeting Cambodia, but their modus operandi has changed," he said.
Technology is creating new headaches for those trying to stop the abuse as sex tourists can better prepare their journey in advance.
One Thailand-based investigator told AFP that encrypted chat rooms have long allowed abusers to share images and advice.
But now websites such as AirBnB, which allow people to privately rent accommodation, and video messenger apps like Skype are making it possible to locate both victims and privacy before abusers even arrive land in a country.
"Yes that's happening," said Meas, "Technology helps them. We have to increase our expertise in this field."
Over the years Western embassies have ramped up co-operation with authorities in Southeast Asia in a bid to stop their nationals from abusing children.
Most European and North American embassies in Bangkok, for example, have police officers stationed in them dedicated to anti-paedophile work.
But as another foreign Bangkok investigator, who asked not to be named because they work with Thai police, commented, there has been much less co-operation from Asian countries whose nationals visit Cambodia in greater numbers than Westerners.
"There's been decent co-operation over recent years with some embassies," the investigator said. "But I can't say they same for the Japanese, Chinese and South Koreans. And they have a much bigger footprint in the region."
Voluntourism and orphanages are another risk area, as they give paedophiles a seemingly innocuous route to their victims instead of approaching them on the street.
A former director of APLE was himself jailed earlier this year for abusing 11 children under his care at a Phnom Penh orphanage he ran after leaving the charity in 2005.
He insists he was set up by APLE investigators, a charge the charity denies and the court rejected.
Some blogs in Cambodia, mostly written by foreign expats, have accused APLE of overzealously targeting foreign men who may be innocent and simply trying to help poor locals.
But Meas rejects this. Walking through a Siem Reap park that is a known hotspot, he says legal cases are only brought after lengthy investigations and once compelling evidence has been compiled.
On a bench in the distance a caucasian man is playing a ukelele to two Cambodian children.
"It's difficult," he said. "He could be a completely innocent and a good person. But that's the kind of interaction we must look out for and follow up."
And with that he calls an agent on his phone.