Corruption is rife in the Southeast Asian kingdom, with officials often accused of accepting small bribes and payoffs, but sums of this magnitude are rare.

The approximately US$57 million was discovered in multiple accounts held by three women and a man who worked in the revenue department in Samut Prakhan province near the capital Bangkok.

The National Anti-Corruption Commission (NACC) has referred the case to the attorney-general’s office and requested that the Criminal Court for Corruption also investigate.

The four were “unusually wealthy”, said Sornchai Chuwichian, assistant secretary-general and deputy spokesman of the NACC.

Their listed assets – including their bank deposits – did not match their government incomes, Sornchai said in an NACC statement on Monday.

None could explain the source of the money, Sornchai said.

The man, Danai Damrongchaiyothin, had US$31 million in seven accounts, while one of the women held more than US$14 million in five accounts.

A starting salary for a revenue official is less than US$450 per month.

All four have been dismissed from their government posts, according to the NACC statement. It did not mention whether they had been charged or arrested.