Senators will wait for the outcome of Sunday's election before deciding to cast their votes for the next prime minister, they said, while expressing their readiness to support a candidate from whichever party that wins the most House seats.
A source at the Senate told Bangkok Post that the 250 members of the Upper House -- mostly former civil servants, police officers and military personnel -- are now divided into three groups.
One group of 120 senators backs Prime Minister Prayut Chan-o-cha while another group of 80 supports Deputy Prime Minister Prawit Wongsuwon, and the other comprises 50 independent senators whose preferences were not clarified.
Main contenders: Paetongtarn Shinawatra with Strettha Thavisin, two of the three Pheu Thai Party prime ministerial candidates, with supporters at the party's final campaign rally at Impact Arena, Muang Thong Thani in Nonthaburi on Friday.(Pattarapong Chatpattarasill)
Under the constitution, the 250 senators appointed by the now-defunct National Council for Peace and Order (NCPO) are allowed to join MPs in electing a prime minister in parliament.
It will be the second and last time they will co-elect a prime minister after today's election. In the 2019 election, they joined MPs in voting for Gen Prayut.
The constitution stipulated that the Senate would serve for a five-year transitional period following the 2019 general election. Their five-year tenure will end next year.
Wallop: Opting out of PM vote
Senator Wallop Tangkananurak said that he would abstain from voting for a prime minister in parliament but said that, in principle, any party that wins the most seats should have the right to form a government and nominate its PM candidate for a vote in parliament.
"But most senators agreed that whichever party becomes the government must protect the main institution [the monarchy],'' Mr Wallop said.
Senator Somchai Swangkarn said most senators agreed they will wait for the outcome of Sunday's election before making a decision about who they will vote for.
"We will wait and see which party will nominate who for prime minister. In the previous election, the Pheu Thai Party named its PM candidates -- Chadchart Sittipunt and Khunying Sudarat Keyuraphan.
"It later turned out that Pheu Thai decided to support Thanathorn Juangroongruangkit, the former leader of the now-defunct Future Forward Party, in a prime ministerial vote instead of its own candidates."
Mr Somchai said the senators would stand by the proper principles in choosing a prime minister as this will be the Senate's final vote for one.
He said any nominated by a party must have integrity, vision, leadership skills and knowledge to steer the country forward.
Somchai: Wait-and-see stance
Mr Somchai said he believed it would take about two months for parties to negotiate a coalition before a new government can take shape.
Senator Wanchai Sornsiri agreed that any party that wins a majority of House seats should nominate a PM candidate for a vote in parliament.
He said the candidate should not have a tarnished reputation.
"In principle, senators should vote for a prime ministerial candidate nominated by the party with the most House seats if the candidate meets the qualifications.
"I don't think parties will nominate anyone with a bad record,'' Mr Wanchai said.
"It will be much easier if parties can gather the support of a combined 376 MPs [more than half of the combined 750 members of the Lower and Upper Houses]."
Parties may also only need the support of 300-310 MPs, with the backing of 70-80 senators, to form a coalition and nominate a candidate for a vote in parliament, he added.
Senator Kittisak Rattanawaraha said he would not vote for a candidate from any party that seeks to revise the lese majeste law.
He added he would not support a minority government, saying this would add fuel to the fire, plunging the country into political chaos.
Kittisak: Lese majeste concerns