Rival camps in Thailand’s new parliament made their case for the kingdom’s next prime minister on Wednesday ahead of a vote expected to return junta chief Prayut Chan-O-Cha to power and brush off the challenge of a charismatic billionaire leading the anti-military bloc.

Prayut, who seized power in 2014, is all but assured of completing his transformation from coup maker to civilian leader with the support of 250 senators handpicked by the junta.

His only rival is anti-junta coalition candidate Thanathorn Juangroongruangkit, whose alliance appears destined to fall short of the 376 lower house votes needed to clinch the premiership.

He has also been besieged by court cases that could see him banned from politics and jailed despite his Future Forward party scooping up millions of votes in a March poll.

Thailand remains bitterly divided after 13 years defined by coups, violent street protests and short-lived civilian governments.

At their root is a rivalry between an arch-royalist conservative establishment – buttressed by the courts and the army – and pro-democracy parties supported by many in the lower and middle class.

Reflecting those fault lines, parliament quickly descended into a fiery debate that could drag on for hours as MPs seize the chance to speak.

Thanathorn, unable to enter the building due to the complaints against him, made an impassioned speech near the entrance.

“We [Thais] are like frogs in boiling water . . . when we realise how quickly the world changes it will be too late,” he said, railing against the junta’s handling of society and the economy.

Critics say the famously gruff 65-year-old ex-army chief Prayut represents a narrow elite and lacks the vision to govern as a civilian leader.

Earlier former prime minister and ex-Democrat Party leader Abhisit Vejjajiva resigned his seat in protest at his party’s decision to support Prayut.

Lawmakers from Pheu Thai, the political machine tied to self-exiled premier Thaksin Shinawatra, took advantage of the rare opportunity to criticise Prayut during the televised proceedings.

Prayut has “obsolete ideas”, MP Cholnan Srikeo said, that would endanger the country.

But supporters say he is a stabilising figure who can steer Thailand away from its perennial political crises.

“I am going to vote for General Prayut,” said Mongkolkit Suksintharanon, head of junta ally the Thai Civilised Party. “Thanathorn has no experience.”

Unexpected third force

The March election was cast as a choice between a tethered democracy led by a junta in civilian clothes and parties aligned with former premier Thaksin and his sister Yingluck, whose administration was toppled in 2014.

But an unexpected third force emerged, led by billionaire auto-parts scion Thanathorn.

His Future Forward Party won 81 seats to become Thailand’s third largest party, shaking up a political scene long dominated by the army and their nemesis the Shinawatra clan.

The social media savvy 40-year-old is now heading a coalition with the Shinawatra’s main party – Pheu Thai – and five others.

Analysts say Thanathorn represents the greatest challenge to the junta and its establishment allies, with his strident calls to bridge the kingdom’s chasmic social inequality and end the military’s influence over politics.

But Thanathorn is weighed down by the legal problems that led to his suspension from parliament.

He has said the complaints are politically motivated.

Assuming the Thai senate votes with the junta, Prayut, who did not attend Wednesday’s session, only needs 126 in the lower house.

Analysts say troubles lie ahead for a military man unused to debate and consensus-building.

“Politicians will try to make scenes . . . to expose Prayut,” said Titipol Phakdeewanich, a political scientist at Ubon Ratchathani University.