A growing number of senators are backing Move Forward Party leader Pita Limjaroenrat's bid for prime minister.

Senator Sathit Limpongpan said he will support a government coalition which manages to secure more than 250 House seats, or half of all the seats. He joins at least 14 other senators reportedly ready to back Mr Pita's bid to become prime minister.

An MFP-led alliance has so far gathered 313 seats from eight parties as it works to build a government bloc. The next step is to win at least 376 votes in the 750-seat parliament, which comprises 500 MPs and 250 senators.

Concerns were mounting as the MFP had been critical of some parties, calling them "pro-dictatorship", as well as the coup-appointed Senate. But some members from the Democrat Party, which is not part of the MFP-led coalition, have said they were lobbying to back Mr Pita to "preserve democracy".

Wanchai Sornsiri, an outspoken senator, denied opposing Mr Pita's bid, saying he was misunderstood.

He vowed to elect anyone able to gather more than half of the votes in the House of Representatives as premier.

A major problem several senators have with the MFP is the party's stance to amend or repeal Section 112 of the Criminal Code, or the lese majeste law.