Srettha Thavisin, Thailand’s prime minister, has been ousted in a court ruling after less than a year in office, throwing the country into fresh political turmoil.

The constitutional court’s ruling on Wednesday marks the fourth time it has removed a prime minister in 16 years, and comes a week after its decision to dissolve the main opposition Move Forward party.

The constitutional court ruled that Mr Srettha had “no honesty and breached ethical standards” in the appointment of an adviser – Pichit Chuenban – who allegedly committed bribery 16 years ago and was imprisoned for contempt of court in 2008.

Many Thais will likely see the ruling as yet another example of an overzealous military establishment loath to loosen its grip on power.

The outcome was a close call: judges voted five to four against the prime minister, but the decision cannot be appealed against.

“I respect the verdict,” Mr Srettha, who took office in late August 2023, said after the ruling.

“I reiterate that for the almost one year I have been in this role, I have tried with good intentions to lead the country with honesty.”

Mr Srettha came to power after the royalist-military establishment resisted last year’s election results.

The reformist Move Forward party won the most votes and seats, but was blocked from taking power because of its pledge to reform Thailand’s lèse-majesté law, which protects the monarchy from criticism.

After weeks of messy negotiations, Mr Srettha and his Pheu Thai party emerged to lead a coalition government.

It was a remarkable result for Mr Srettha, a 62-year-old property tycoon, who entered politics a few months before the May election. It also put an end to nine years of military-backed governments.

However, his position was seen as fragile from the start. Analysts say the military preferred Pheu Thai, long the nemesis of the establishment, over the reformist Move Forward party.

Many suspect back-room deals were behind the party’s rise as Mr Srettha’s benefactor – the former prime minister and past Manchester City owner, Thaksin Shinawatra – returned from 15 years of exile the same day Mr Srettha took office.

But in June, Mr Thaksin was indicted in a royal defamation case in the first sign the arrangement was starting to unravel.

“History seems to be repeating itself,” Napon Jatusripitak, a visiting fellow at the ISEAS Yusof-Ishak Institute, a think tank based in Singapore, said.

He added that the other three premieres – two in 2008 and one in 2011 – were forced out for less.

“Samak Sundaravej was removed by the court for hosting a cooking show [in 2008].”

Like Mr Srettha, those previously removed were aligned with Mr Shinawatra – including his sister Yingluck. The billionaire was pushed out from office in a military coup in 2006 and fled Thailand. However, he remained a force in the Pheu Thai party, exerting influence behind the scenes.

Though some have described Mr Srettha as Mr Thaksin’s puppet, it was believed the semblance of a unified, stable government would endure for longer, especially as many, particularly young Thais have grown angry with the cycle of coups, political instability and economic inertia.

“I think that this verdict comes as a surprise to most Thai political observers,” Mathis Lohatepanont, a political analyst, said.

“I believe that the coalition will endure – the grand compromise between the Thaksinites and the conservatives is still necessary to keep the new People’s Party out of power – but it has certainly now been shaken,” he added, referring to the new iteration of Move Forward formed last week.

It is not yet clear who will replace Mr Srettha, though Mr Thaksin’s 37-year-old daughter Paetongtarn Shinawatra is one of the candidates. Parliament has to choose the country’s new leader from a list of options submitted before the  2023 elections; among the other options is Prawit Wongsuwan, a former army chief who was involved in the last two coups.

In the interim, the cabinet will remain in place on a caretaker basis. But the political turmoil has already hit the country’s struggling economy, which has endured a decade of below 2 per cent annual growth and sky-high household debt. After Wednesday’s announcement, the nation’s benchmark stock index fell by 1.3 per cent.