Bhumjaithai has insisted the party will support a prime minister from a political party amid speculation it might back Gen Prayut Chan-o-cha following a high-profile visit of the prime minister to Buri Ram province last week.
Deputy secretary-general Supachai Jaisamut said on Monday an insider prime minister would be his party's first choice.
"But if it's not possible [to get an insider PM], we must accept that we have to look at an outsider as stipulated in the constitution," he said.
If a PM cannot be agreed on, the National Council for Peace and Order (NCPO) is constitutionally required to continue running the country until Parliament chooses one, he said.
"It's therefore critical that a prime minister be chosen as soon as possible."
In any case, he said his party could make the decision only when election results were known.
Commenting on the upcoming fourth anniversary of the coup next Tuesday, Mr Supachai said the coupmakers had come a long way from their roots.
"They came to ease the deep political divide at the time and prevent a bloodshed. But after a while, it wanted more than that -- to create 'a better country' through the constitution, national reform and national strategy.
To preserve its legacy, the NCPO seems to have decided to transform itself into a player from the rule-maker it portrayed itself to be over the years, he continued.
"Judging from recent moves -- a display of support for Gen Prayut as the next PM, especially by his deputy Somkid Jatusripitak, and news a party was set up to support the NCPO and Gen Prayut -- we believe Gen Prayut will become a politician.
"It begs the question then how they would deal with the constitution and laws designed to cripple and weaken politicians now that they too become players," he said.
Asked whether in his view the four years of national reform were a waste of time and resources, Mr Supachai said: "At the very least, it stopped people from fighting each other."
"If Gen Prayut joins a party, we can work together. Bhumjaithai stands ready to cooperate in the best interests of the people and the country," he said.
Speculation has been rife that Palang Pracharat is a new party set up for Gen Prayut by Mr Somkid and his right-hand man and industry minister, Uttama Savanayana, so it could present him as a PM candidate. That way, he would be qualified as "an insider PM".
Gen Prayut was invited to join the party not as an MP candidate but as its chairman of the advisory board. He has remained tight-lipped on whether he would accept the offer.
Two people applied to set up a party under the name Palang Pracharat on March 2. They were Chuan Meechan, chairman of the Khlong Latmayom floating market community in Bangkok, and Col Suchart Chantarachotikul, an ex-Songkhla MP of New Aspiration party and former member of the now-defunct National Reform Steering Assembly.
