"I recently travelled to Singapore and found Wee Hock Kee, a key broker in the CTX 9000 procurement contract," he said.

Alongkorn also said he would submit additional evidence tomorrow to help the investigative panel appointed by the Assets Examination Committee (AEC).

He said he suspected that deposed prime minister Thaksin Shinawatra and former transport minister Suriya Jungrungreangkit were involved in the alleged irregularities.

The graft investigation into the CTX deal should focus on seven points, including project loopholes, suspicious equipment specifications, the inflated budget, the waiver of the bidding process and the lopsided hiring of subcontractors, he said.

Worapoj Yasadatt, managing director of Patriot Business Consultants, a key subcontractor in the CTX contract, yesterday said that he was ready to be a witness for the investigation. He also called on other subcontractors not to pay the final amount of "tea money" on the project.

In another development, AEC spokesman Sak Korsaengreung said the investigation into the Ratchadiphisek land transaction involving Thaksin's wife Khunying Pojaman Shinawatra may have hit a stumbling block.

The AEC has ruled that Pojaman bought the plot illegally due to a conflict of interest because Thaksin was the ultimate supervisor for the liquidation of state property, but the interim government sees nothing wrong with the deal, said Sak.

He said he was not optimistic that the AEC could get to the bottom of corruption because many interim government ministers had served under the deposed government.

"Finance Minister Pridiyathorn Devakula is an example. He used to oversee this case and guaranteed that Pojaman's land purchase was completely legal," said AEC secretary Kaewsan Atipho.

However, Kaewsan said the AEC had been working independently, without interference from the government, since its establishment.