Palang Pracharath Party (PPRP) leader Uttama Savanayana says any party that can gather enough support from other parties, which together have more than half of House seats, should get the first chance to form a coalition government.
He was responding to a reporter's question about whether a party that wins the most seats, if not a majority, in the House of Representatives should be allowed to form a government first as has generally been practised.
A party that wins more than half the seats can form a majority government by itself.
Political observers noted that no single party contesting this election is expected to win a simple majority.
As such, major parties are expected to begin manoeuvring to ensure that they can form a core part of the next coalition government.
"The PPRP's stance is that any party that can first gather support from other parties, which together have more than half of House seats should have the right to form a [coalition] government first,'' Mr Uttama said.
Meanwhile, parties agreed they should unite to stave off the Senate's influence in selecting a prime minister after the election.
Suwat Liptapanlop, chief adviser of the Chartpattana Party, said no party should fear the Senate which has only 250 members, as opposed to 500 MPs.
If the parties could strike a compromise and are on the same page in voting for a prime minister, the Senate's vote would not make a difference, Mr Suwat said. The House of Representatives and the Senate will vote together to select a candidate from among those proposed by eligible parties to be prime minister.
A successful candidate would need the support of at least 375 members of both Houses.
Mr Suwat said the next government will need the support of at least 300 MPs to maintain its stability. Meanwhile, Future Forward Party (FFP) leader Thanathorn Juangroongruangkit echoed Mr Suwat's view.
He suggested that if every party that wins a seat in the election, except the pro-regime PPRP, stands united on the leadership question, the Senate could be stopped from having a decisive influence over the pick for prime minister.
The PPRP has nominated Prime Minister Prayut Chan-o-cha as its sole prime ministerial candidate. The party is pitted against several others in the so-called "democracy camp" including the FFP. The parties have accused the PPRP of being a vehicle for prolonging the regime's grip on power.
Mr Thanathorn said on Thursday that who will make the cut as prime minister post-election hinges on how many seats the PPRP wins in the poll.
The PPRP would need to take in more than 124 seats and when that combines with the support of 250 senators, Gen Prayut would receive at least 375 votes between both Houses, securing his election as prime minister.
