But on Sunday, Pita Limjaroenrat, the leader of Move Forward made it clear that the amendment was still high on his party’s agenda, saying they now have enough members of Parliament to push it forward.

“So it’s not conditional, it’s already absolute that we are going with it,” he said.

Mr. Pita, 42, a former businessman, was fielded as Move Forward’s leader after the country’s Constitutional Court dissolved the party’s previous iteration, the Future Forward Party, in 2020, and barred the party’s senior executives from politics for 10 years. A graduate of Harvard’s Kennedy School of Government and the Massachusetts Institute of Technology, Mr. Pita is a charismatic speaker, who called on voters to create “a new history in Thai politics.”

His background as a technocrat contrasts with the leading contender from Pheu Thai, which has sought to promote Ms. Paetongtarn, Mr. Thaksin’s youngest daughter.

Ms. Paetongtarn, an executive in her family’s hotel management company with little political experience, was selected to run after her father said people “wanted to see a Shinawatra family representative as a force in the party.”