Education officials admit that some foreigners applying for teaching jobs falsify their credentials and many schools fail to carry out proper background checks on applicants.
Fairfax Media revealed last week that a simple Google search would have found that 59-year-old Walbran raped and sexually molested children as young as eight on the Indonesian island of Lombok over a nine-year period.
The Sydney man turned up teaching at Narinukun international school in Ubon Ratchathani, 630 kilometres from Bangkok, in April.
Suthep Chittayawong, deputy secretary of Thailand's Office of Basic Education Commission, said notices have been sent to all schools ordering background checks, including on any criminal convictions and the authenticity of academic qualifications.
He said some foreign applicants falsify their credentials because fake academic documents are easily obtained in Thailand.
"I know some schools choose to hire foreign teachers first and run background checks on them later," Mr Suthep told the Bangkok Post.
"This is because language teachers are in high demand and the checking process usually takes time and is expensive for the schools."
Mr Suthep said an investigation is underway to determine how Walbran, a former head of school at the Australian International School in Jakarta, was able to get a job in Ubon Ratchathani despite publicity about his past crimes.
The secretary-general of Thailand's Private Education Commission Office, Adinan Pakbara, also warned private schools to tighten screening processes.
"Foreign embassies, the immigration bureau, the police and schools themselves should share information," he said.
Tens of thousands of foreigners teach in Thai schools, many of them Australians.
Fairfax Media revealed that Walbran left Australian unnoticed early this year after failing to register on Australia's National Child Offender Register after being deported from Indonesia, where he served just over two years of a three-year jail sentence for child sexual abuse.
Walbran will be deported from Thailand on the grounds of bad character if police do not find evidence that he committed offences in the country.
He is being held in an immigration detention cell.