Thailand's Constitutional Court on Wednesday removed Prime Minister Srettha Thavisin from his position after less than a year in office for breaching ethics rules by appointing a lawyer who had served a jail term to his cabinet.

The case against Srettha centers around the appointment of Pichit Chuenban as a minister of the Prime Minister's Office. In 2008, Pichit was sentenced to six months' imprisonment on charges of attempting to bribe a court official.

Although Pichit resigned from the cabinet in May, a decision seen as a bid to spare Srettha from legal trouble, the court pressed ahead with the case initiated by a complaint from a group of 40 senators.

The Constitutional Court judges began their deliberations at 9:30 am on Wednesday. The nine-judge bench voted 5:4 to dismiss Srettha from office. Srettha did not attend the hearing due to prior work commitments but sent his secretary-general Prommin Lertsuridej.

The cabinet must also resign but will stay on in a caretaker capacity with Deputy Prime Minister and Commerce Minister Phumtham Wechayachai taking over as caretaker prime minister, according to Wissanu Krea-ngam, the PM's adviser and a legal expert.

The parliament will convene on Friday for a special meeting to choose a new prime minister, the legislature announced on its website, following the court's decision.

According to parliamentary rules, a candidate nominated for prime minister must win the support of more than half of the lower house, which currently has 493 members.

There are several potential candidates, including Pheu Thai party leader Paetongtarn Shinawatra, Interior Minister Anutin Charnvirakul, Energy Minister Pirapan Salirathavibhaga and Prawit Wongsuwan, an influential former army chief who was involved in the last two coups.

Local media reported that Srettha visited a Buddhist temple on Wednesday morning, where his mother's cremation ceremony was held last week. He told reporters he had slept well and would carry on with his normal schedule for the day, saying he was not unduly worried about the court case.

Srettha said after the ruling that he respected the court verdict. "I performed duties to the best of my ability and adhered to ethical principles throughout my nearly one-year tenure in office."

As Pheu Thai's prime ministerial candidate, Srettha received majority approval in parliament on Aug 22 last year.

In the past two decades, Thailand has witnessed several prime ministers being ousted by legal decisions and coups.

Some political experts believe that it is likely that Pheu Thai would still have the clout to lead the next administration.

"The coalition remains united," said Olarn Thinbangtieo, deputy dean of Burapha University's Faculty of Political Science and Law. In an interview with Reuters, he said there may be some impact on confidence, but that would be in the short term.

Xinhua and agencies contributed to this story.