With the impeachment of Prime Minister Srettha Thavisin by a court ruling after less than a year in power, Thailand once again plunged into political turmoil.

Reading out the Constitutional Court’s decision on Wednesday, Justice Punya Udchachon said the judges voted by a 5-4 margin to dismiss Srettha from the Pheu Thai Party because he had “lacked honesty and violated ethical standards” by appointing a person with a criminal conviction to his cabinet.

Udchachon said the property magnate had failed to discharge his duty with integrity and “grossly” violated ethics because he must have known about former lawyer Pichit Chuenban’s criminal record when he appointed him as a minister in his office in a cabinet reshuffle in April.

Pichit, who was sentenced to six months in prison in 2008 for attempting to bribe court officials with 2 million baht ($55,218) in a paper bag, resigned from his post in May to protect Srettha.

But that same month, the Constitutional Court’s judges voted 6-3 to accept a petition from 40 senators to remove Srettha from office, issuing Wednesday’s ruling at the end of their investigation into the allegations.

With Srettha’s dismissal, he becomes Thailand’s fourth prime minister in 16 years to be removed from office following a ruling by the Constitutional Court.

Outside his office, he told reporters that while he “respected the verdict,” he was “sad” to be called dishonest.

According to Khemthong Tonsakulrungruang, a lecturer at the Faculty of Political Science at Thailand’s Chulalongkorn University, the decision came as a surprise to many Thais.

“Most people speculated that Srettha would be acquitted, so it is a big shock that I think many people were not prepared for,” he told Al Jazeera. “The allegation itself is very trivial. (Appointing Pichit) is certainly a bad political decision, but to say that he is acting dishonestly or criminally is going too far for most people.”

Khemthong said the ruling shows that “no office is safe in this country” and that “there is always some legal trap that anyone can fall into.”

Who could replace Srettha?

Pheu Thai is currently scrambling to find a replacement candidate. The Thai parliament is scheduled to convene a special session at 10:00 a.m. (03:00 GMT) on Friday to vote on the issue.

The party can only nominate those who have been nominated as candidates for the post of prime minister before the 2023 election.

Ken Mathis Lohatepanont, a Thai political commentator and doctoral candidate in the political science department at the University of Michigan, told Al Jazeera that 75-year-old former Pheu Thai Party justice minister Chaikasem Nitisiri is currently the favorite for the nomination.

Another promising candidate is 37-year-old Pheu Thai leader Paetongtarn Shinawatra, the daughter of former Prime Minister Thaksin Shinawatra and niece of Yingluck Shinawatra, also a former Prime Minister. Thaksin was overthrown in a military coup in 2006, Yingluck in 2014.

Lohatepanont described Chaikasem, who was Pheu Thai’s candidate for prime minister in 2019 and 2023, as a “secret favourite”. Few had considered him as a potential leader due to reports of his poor health. But with his condition reportedly improving in recent months, the veteran politician is now a “logical choice for Pheu Thai”.

“(Chaikasem) keeps the pressure off Paetongtarn, who many consider too inexperienced or too valuable to Thaksin to risk in this delicate situation,” Lohatepanont said.

“(He) also retains the office of prime minister with Pheu Thai itself, without having to allow another party like Bhumjaithai to take over the government,” he added, referring to another major party in the Pheu Thai-led coalition.

Other members of the coalition, which came to power under controversial circumstances a year ago, will also field candidates, but not all are expected to do so and there will be negotiations between the parties, trading political support for cabinet posts.

If the coalition – and this seems most likely at present – puts forward a candidate from the Pheu Thai Party and that candidate receives the support of parliament, the “government will almost certainly remain (the same),” Lohatepanont said.

“In principle, there should be considerable personnel and political continuity,” he said.

Party maneuvers

Srettha’s dismissal was the second major ruling by Thailand’s Constitutional Court within a week, after it dissolved the Move Forward Party (MFP) on August 7. The judges ruled that the progressive party had violated the country’s constitution with its proposed reforms to Article 112 of Thailand’s Penal Code, which restricts criticism of the monarchy.

The MFP won a surprise victory in Thailand’s 2023 general election, relying on a progressive program that appealed to younger voters. The MFP won 151 seats in Thailand’s 500-seat House of Representatives, 10 more than the second-placed Pheu Thai Party, and attempted to form a coalition with other pro-democracy parties.

But the military-appointed Senate used the powers granted to it by a constitution drafted by the military in 2017 to block the MFP from power, while suspending its leader, Pita Limjaroenrat, as a member of parliament and barring him from serving as prime minister.

Pheu Thai then formed its own 11-party coalition under Srettha, which included government and military parties and excluded the MFP. This move was seen by many as a betrayal of the democracy movement after Srettha broke his election promise not to cooperate with the military-affiliated parties Phalang Pracharat and United Thai Nation.

Their inclusion in the coalition was believed to be part of a political deal to shorten the prison sentence of Pheu Thai founder Thaksin. Thaksin will return to Thailand in 2023 after living in self-imposed exile for 15 years to avoid defamation charges by the royal family.

Khemthong cited Thaksin, who was again charged with royal defamation in June, as a possible explanation for the Constitutional Court’s surprise ruling against Srettha. He said people had speculated that the move was a “rebuff for Thaksin” and that “internal political considerations may be at play.”

In any case, he described Thaksin as someone who was “held hostage” in the situation, meaning the Pheu Thai party was unlikely to challenge the ruling.

“Thaksin cannot leave the country. His bail can be revoked at any time and he can be physically detained. So there are big restrictions on him,” he said.

Last week’s Constitutional Court ruling confirmed the MFP’s rapid decline, mirroring what happened to its predecessor Future Forward after its strong showing in the 2019 elections. The ruling dissolved the party and banned its executive committee, including Pita and current chairman Chaithawat Tulathon, from political activity for 10 years.

But 143 of the party’s MPs were able to retain their parliamentary seats by switching to the Thinkakhao Chaowilai Party and renaming it the People’s Party. Rangsiman Rome, one such former MFP member and now a People’s Party MP, told Al Jazeera that Wednesday’s ruling against Srettha was a “court coup”.

He added that Move Forward was interested in working with Pheu Thai to “put an end to this madness”, referring to the interference of the military and ruling elite in politics.

“This should be a good opportunity for us to rethink the constitution, our constitution, which was written by the coup plotter,” he said, referring to the 2017 bill drafted by then-army chief and current Prime Minister Prayuth Chan ocha.

Rome said People’s Party MPs would assess the mood among Pheu Thai members in parliament on Friday, but he warned that he was not optimistic that a new alliance could be formed given the serious criminal charges facing Thaksin.

“If the Pheu Thai Party tries to challenge power in Thailand, I am not sure they will have a free hand if Thaksin has a case like this,” he said.