Senators are divided over whether to support Srettha Thavisin if Pheu Thai nominates him for the prime ministerial vote in parliament.
Senator Wanchai Sornsiri said he was optimistic that most senators would support Pheu Thai and its prime ministerial candidate now it had split from the Move Forward Party (MFP), whose policy to amend Section 112 of the Criminal Code, or the lese majeste law, was opposed by many senators.
Only when Pheu Thai manages to gather support from more than 250 MPs in forming a government will he be confident a candidate from the bloc will get sufficient backing from the Senate.
Senators believe tax allegations against Mr Srettha could still be looked into, he said.
This week, whistleblower Chuvit Kamolvisit implied there had been land sale tax evasion in Sansiri's purchase of land on Sarasin Road in Bangkok in August 2019, when Mr Srettha was still CEO.
Chuvit implied that Mr Srettha and Sansiri colluded with the landowners to evade 521 million baht in taxes on the developer's purchase of the block of land.