Thailand's Constitutional Court will decide on Wednesday whether Prime Minister Srettha Thavisin should be kicked out of office over his appointment of a cabinet minister with a criminal conviction.
Srettha is accused of breaching ethics rules by appointing Pichit Chuenban, a lawyer closely associated with the family of billionaire former prime minister Thaksin Shinawatra, to his cabinet.
The ruling, expected around 3:00 pm (0800 GMT) comes a week after the same court dissolved the main opposition Move Forward Party (MFP) and banned its former leader from politics for 10 years.
Thailand has a long history of instability and judicial involvement in politics, with the Constitutional Court dismissing prime ministers in the past.
However, observers say the signs look positive for Srettha, who has denied any wrongdoing.
Pichit, who was sentenced to six months' jail in 2008 for a graft-related offence, quit the cabinet in a bid to save Srettha but the court pressed ahead with a case initiated by a complaint by senators appointed by Thailand's former junta.
Srettha said he was getting on with his job as prime minister and did not plan to watch the judges give their ruling.
"I have done my best and sent a closing statement, now it depends on the justice system," he said on Tuesday.
"I have a schedule of meetings with government agencies. I believe the team will inform me (about the verdict)."
Srettha came to power less than a year ago at the head of a coalition led by his Pheu Thai party, of which Thaksin remains a key patriarch figure, after striking a deal with army-linked parties.
The court case highlights old divisions in Thai politics between the conservative, pro-royalist, pro-military establishment and progressive parties such as Pheu Thai and its new rival MFP.
The 40 senators who brought the complaint were all appointed by the military junta that ousted an elected Pheu Thai government in a coup in 2014.
The senate also played a crucial role in thwarting MFP's attempt to form a government after it won the most seats in last year's general election.
Senators alarmed by its pledges to reform lese-majeste laws and break up powerful business monopolies refused to endorse MFP's then-leader Pita Limjaroenrat as prime minister and the party was forced into opposition.
Srettha faces a tough time even if he survives the court ruling, with several key policies facing significant opposition and a majority of Thais rejecting his agenda, according to a June poll.
His proposals to recriminalise cannabis and distribute 10,000 baht ($280) to more than 40 million Thais have sparked controversy both nationally and within his coalition.
