Paedophile travelling on a New Zealand passport detained in Thailand

Police detained Peter Dundas Walbran, 59, of Sydney who was flying using a New Zealand passport. Photo / Mark Mitchell

An Australian convicted paedophile travelling on a New Zealand passport has been detained in Thailand on suspicion of child sex offences.

Police detained Peter Dundas Walbran, 59, of Sydney, on Wednesday at a secluded school 616km from Bangkok where he had been working as a teacher. He was not arrested.

Police had been tracking Walbran for 18 months, the Daily Mail reported, after receiving a tip the school had hired him in May and he was overseeing its 70 international students. The school has 4000 students on its roll.

Walbran told the pack of photographers and journalists, who gathered outside the school to capture him being led away, that he was "okay" before becoming increasingly aggressive.

In October 2011, Walbran, a former head of the Australian International School in Jakarta, was extradited from Australia to Indonesia following a request by the country's government. The next year he was jailed for the rape and molestation of Indonesian boys, some as young as 8.

He served two years of a three-year sentence before being deported back to Australia in April last year.

Walbran then flew to Thailand through New Zealand, using a Kiwi passport, which enabled him to avoid Australian travel alerts for convicted paedophiles. He also failed to complete the process of registration with Australia's National Child Offender Register, Thai investigators told AAP.

He is being held pending investigation by police and investigators said if they failed to uncover any local offences, he would be deported to New Zealand.

The raid came soon after new legislation in Thailand made possession of child abuse material illegal.

Prime Minister John Key today said he doesn't know how Walbran obtained a New Zealand passport.

"My advice at this stage is Mfat [Ministry of Foreign Affairs and Trade] doesn't know about the individual," he said.

"It's quite possible that it's legitimate. There are people that [sic] have multiple passports because they have multiple citizenship. So there are lots of people who travel on both an Australian and New Zealand passport and might theoretically do that at one time. "But if it's an illegal passport, that's a very different issue but I don't have any advice about that."