Thanathorn was not present for the vote. The leader of the Future Forward party is currently barred from performing the duties of an MP by the Constitutional Court pending the case involving his stake in a media company.

Former Democrat party leader Abhisit Vejjajiva also failed to attend. Abhisit resigned shortly before parliament convened on Wednesday morning in protest of the party’s alliance with the pro-Prayuth Palang Pracharat.

Thanathorn held a quick press conference at the temporary parliament after the voting was over.

“Today we cannot stop the dictatorship but we have not been beaten. I had hope yesterday. The seven-party alliance fought until the last minute. We did not give up along the way,” he said.

“It will be a long way to democracy for Thailand but we believe the people will win in the end. Dictatorship will not resist the wind of change. I’m disappointed. I’m sad. But it is expected. I’m going to work harder. Tonight told us one thing that we have not worked hard enough.”

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The democratic front MPs, an anti-junta seven-party alliance, brought up issues – including the 2014 coup, the appointment of the senate, the military-controlled constitutional drafting committee, repeating postponements of the polls and the suppression of press freedom and political activism by the military government – to indicate that Prayuth is unfit to continue in the post because he does not adhere to democratic principles in his efforts to prolong power.

On the other hand, several Palang Pracharat MPs said that the coup was necessary to end anti-government demonstrations that can lead to violence and that Prayuth is the only person that can mend the political divide Thailand has been mired in for over a decade.

Prayuth, then army chief, led a military intervention that overthrew the Yingluck Shinawatra administration, citing corruption and negligence of duties.

Observers have said the 2014 coup was meant to put a permanent end to the Shinawatra influence in Thai politics after the 2006 coup – which ousted Thaksin Shinawatra – failed to do so, as the political clique related to the former prime minister has won every election since, including a landslide in 2011 that propelled Thaksin’s sister Yingluck to power.

The senators, who are picked by the junta, debated in favour of Prayuth. Wanchai Sonsiri, a senator, said Prayuth would be a better prime minister than Thanathorn because he has more experience and has never been engaged in any lawsuit like the leader of the Future Forward.

Thailand remains bitterly divided after 13 years defined by coups, violent street protests and short-lived civilian governments. At root is a rivalry between an arch-royalist conservative establishment – buttressed by the courts and the army – and pro-democracy parties supported by many of the lower and middle classes.

Prayuth’s time in charge has been characterised by efforts to silence critics and the use of the encompassing Article 44 exercised under the jurisdiction of the National Council for Peace and Order (NCPO), established after the 2014 coup. As soon as the new cabinet is installed, the NCPO will be dissolved.

In the months since the election, negotiations over cabinet positions have been ongoing, with the pro-junta camp approaching MPs to secure votes for Prayuth.

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On Tuesday, Future Forward MPs claimed the party had been offered cash, in one case as much as 120 million baht (US$3.8 million), from pro-junta parties. 

Olarn Tinbangteow, an associate professor of political science at Burapha University, said before the vote that the power invested in the senate would undermine Thai democracy.

“When the appointed senate in Thailand can select a prime minister, it goes beyond the appropriate level of power they should have because they are not an elected body,” Olarn said. “The senate’s role in extending the junta leader’s power then is being institutionalised.”

Palang Pracharat was established last year as a proxy for the junta with the objective of ensuring Prayuth’s transition from coup leader to a prime minister endorsed by an elected parliament.

“[The] Thai junta has not only successfully transformed itself into a military-dominant coalition government … it has succeeded in co-opting enough political parties in support of that coalition government to maintain the appearance of electoral legitimacy,” Paul Chambers from Naresuan University said before the vote.

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Chambers highlighted “an electoral formula favourable to small parties, a junta-appointed senate, an unelected PM, gerrymandering, a judiciary favourable to the junta and intimidation of the parliamentary opposition” as factors designed to keep Prayuth in the top job.

“Ultimately, following the Wednesday vote, the junta’s autocratic control over Thailand will become camouflaged behind the appearance of democracy,” he said.

Additional reporting by Agence France-Presse