Peter Dundas Walbran with police after his arrest in Ubon Ratchathani, Thailand on December 9. Credit:Am Sandford A police investigator said they had seen Walbran with children from his local neighbourhood several times since Monday. "We saw Walbran take a boy from the apartment to a shop on (the) back of his motorbike," the investigator told Fairfax Media. "We are investigating." Walbran is expected to be flown to the capital Bangkok as investigations continue into his activities in Thailand. That Walbran came to be teaching children in Asia again, after being deported from Indonesia to Australia last year, raises questions about the effectiveness of Australia's National Child Offender Register.

Peter Dundas Walbran in police custody. Credit:Am Sandford Melbourne investigator Glen Hulley tracked 59-year-old Walbran to an international school in Ubon Ratchathani, 630 kilometres from Bangkok, where he has been teaching children aged 12 to 17 for eight months. Photographs on the school's Facebook page show children prostrate on the ground in front of Walbran and other teachers in a Thai ritual where students pay respect to their teachers. Police surveillance photos of Peter Walbran riding on a bike in Ubon Ratchatani, Thailand, earlier this week. Walbran was hired to work at the school despite the fact that a simple Google search would have shown him to be a convicted paedophile.

The revelation has stunned teachers at the Narinukun international school, who worry about the impact it will have on students. They fear the school will collapse if furious parents withdraw their children. Peter Walbran, right, arrives in Indonesia in 2011 to face child rape charges. A police undercover operation kept Walbran under surveillance for days, including from an apartment adjacent to one he had been renting for months. Fairfax Media withheld publishing details of Walbran's past crimes until police swooped on his apartment on Wednesday. Students at the Narinukun school pay respect to teachers during a Thai ceremony on June 26, 2015. Peter Dundas Walbran is third from right, wearing blue short-sleeve shirt. Credit:Narinukun international School/Facebook

Police will question a young Thai man who has been living with Walbran in his small third-floor apartment which has no kitchen. Police raided the apartment two days after new legislation came into force in Thailand on Tuesday that criminalises possession of child abuse material, with offenders facing up to 10 years' jail. Students pay respect to teachers during a ritual on June 26 2015. Peter Dundas Walbran is third from right in the blue short-sleeved shirt. Credit:Narinukun international school/Facebook Fairfax Media can reveal that Thai authorities will deport Walbran on the grounds of bad character if investigators find he has not offended in Thailand. Walbran was sentenced to three years' jail on the Indonesian island of Lombok in 2012 for offences that shocked investigators, including the repeated rape and abuse of children over a period of nine years.

A police surveillance photo of convicted child sex abuser Peter Dundas Walbran riding on a bike in Ubon Ratchatani earlier this week. Indonesian authorities alleged that Walbran befriended children on beaches and paid them as little as the equivalent of $3 after committing acts on them that distressed investigators, including one who wept when reading victims' statements. In 1997 Walbran approached an eight-year-old boy who was crying on a beach because he had lost his ankle bracelet and was too afraid to go home, police alleged. Walbran bought him clothes, took him to a waterfall and gave him money before sexually abusing him on many occasions, police said. "Come to my house and I will give you money," Walbran told another 12-year-old boy the same year, police alleged. One victim who was befriended by Walbran when he was 12 told police he was too afraid to talk about what Walbran had done to him until he was 20.

Edi Setiawan, an Indonesian child sex investigator, told Fairfax Media that six children have told him that Walbran abused them on Lombok but only three were prepared to give police statements. Mr Setiawan said that even after being deported to Australia, Walbran emailed one of his victims saying he planned to live in Thailand but would return to Lombok to see him. Mr Setiawan said Walbran offered one of his victims a house and another a motorbike, but they agreed to testify against him after he reneged on the promises. Walbran was suspended in March 2007 from the exclusive Australian International School in Jakarta after police began investigating him for child sex offences outside of the school. Walbran returned to Australia before the investigations were complete and was living at Warriewood, on Sydney's northern beaches, when he was extradited to Indonesia in October 2011, following a request from Jakarta's Law and Human Rights Ministry.

Walbran served just over two years of the three-year jail sentence on Lombok before being deported to Australia in April last year. Mr Setiawan said he visited Walbran in jail two days before his deportation. "He looked angry and kept telling me he was innocent," Mr Setiawan said. Two weeks after arriving back in Sydney on temporary Australian travel documents, Walbran was served papers ordering him to register his Indonesian convictions with Australia's National Child Offender Register. But he failed to do so and left Australia again early this year on a New Zealand passport that he had acquired while in NSW. If Walbran had been on the child sex offender register he would have been required to report his intended travel and Australian Federal Police would have alerted Thai authorities to his arrival in the country.

Mr Hulley, the father of two boys, sold his house, car and business in Melbourne to establish Project Karma, an NGO which partners police, government agencies and other NGOs in Asia to combat child sex exploitation and child trafficking for sexual abuse. He called on the Australian government to cancel the passports of child sex offenders so they cannot travel overseas. "That will raise human rights issues but the offences these people commit are so grave they warrant extreme measures," he said. The Narinukun school cancelled Walbran's work contract on Wednesday. Follow FairfaxForeign on Twitter