Girls working in Pattaya, Thailand. "They move frequently – often between Thailand, the Philippines and Cambodia," he said. But Supagon, whose centre is caring for 41 abused children aged between seven and 17, said he expected to see increasing prosecutions after the establishment of Thailand's Internet Crimes Against Children Taskforce (TICAC), with backing from Interpol and other international police agencies. Thailand's military government set up the taskforce in January last year after experts warned that rising internet use in south-east Asia was fuelling the spread of material that is abusive and sexually exploitative of children. Internet availability in the region has grown to about 50 per cent of the population but the figure rises to 58 per cent in the Philippines, where there is a booming cybersex industry.

Peter Scully inside the Cagayan De Oro court handcuffed to another inmate on his first day of his trial in 2016. Credit:Kate Geraghty In partnership with Philippine law enforcement agencies the International Justice Mission (IJM) has rescued 1275 children and women from sex trafficking over several years. The most notorious case there is that of former Melbourne businessman Peter Scully, a master of the "dark web" who is facing trial on 75 charges, including directing a video involving horrific torture and injuries to an 18-month-old baby. In Thailand, where the problem is growing, internet availability reaches 67 per cent. Neil Walsh, who heads the global cybercrime program of the United Nations Office on Drugs and Crime, said last year paedophiles were spreading, at a "phenomenal" rate, sexually exploitative materials through an overlay of online networks that cannot be easily accessed. "The more we work harder to remove the contents, the more they make it harder to find," he said, adding that Thailand had become the "webcam centre for child pornography," stripping the Philippines of the title.

Speaking on the sideline of a conference on child sex abuse in Bangkok, Jon Rouse, a member of a Queensland police unit that targets online child sex abuse networks across the world, warned the sharing of abusive and sexually child exploitation material will continue to increase in south-east Asia. He cited a survey last year which identified 3600 individual internet addresses in the Thai capital as having shared child exploitation material over just seven days. Australia last year legislated to stop registered child sex offenders travelling overseas in what officials called a "world first" in the fight against child sex tourism. The law will affect an estimated 20,000 registered offenders who have served their sentences but are still under supervision and must report to authorities. But 46 year-old Supagon, who has been tracking child sex abusers in Pattaya for 27 years, said he believes Australians who have never been caught are among foreign predators in Pattaya, where there are several hundred street children.

"We will not stop working to expose these people who come to Thailand to hurt Thai children...they have gotten away with it in the past but their time is coming," he said. Supagon, who is known as Kru Ja, said the abusers account for only a fraction of the millions of visitors to Thailand each year "but they damage our reputation as a good place to [visit]." He said the victims were often street children recruited by Thai brokers who operate in an area of South Pattaya. "I speak with the children and they tell me how they have been abused," Supagon said. "But it is very difficult to get them to testify in court. They are afraid." Almost all the victims were boys, he said.

Loading Supagon said only about 10 foreign child abuse suspects were prosecuted each year in Pattaya, where local authorities have been working to clean up its reputation as a sex tourism destination. Interpol too has expanded its presence in the country to fight child sex abuse, recently hiring former Thai police Lieutenant-Colonel Apichart Hattasin, who for years led undercover operations in northern Thailand targeting foreign paedophiles.