Alongkorn claimed that the alleged corruption also involved a Singaporean company and an influential Thai woman referred to as "Jae", Chinese for "elder sister".

The companies being accused are listed firm Thai Airport Company and Thai Airport Ground Services (TAG). The concessions are thought to be for 10 years, and the money involved amounts to some Bt10 billion, with the contracts signed on April 28 last year, allegedly without bidding.

"I will also ask the AEC to examine the Airport Organisation of Thailand [AoT] board," he said, adding that more nominees were allegedly also involved in the cases.

Attention may also be focused on a Singaporean company by the name of Frobisser, which has reported revenue less than that earned by an ordinary noodle stall but is involved in the concession.

"In 2003 the firm reported revenue of five Singapore dollars, or Bt120. In 2004 its registered income was four Singapore dollars, or Bt100, but surprisingly by the end of 2004 it suddenly had Bt198 million to buy TAG shares," he said, adding that it had been claimed that Thais held 50 per cent of the shares but that was likely to be through a nominee. The house registered by the nominee had been abandoned for some time and has since been demolished.

Alongkorn said he would ask the Department of Special Investigation to press charges against those in the alleged scam.