The Constitutional Court has set Sept 30 for its ruling on when suspended prime minister Prayut Chan-o-cha's eight-year tenure as premier began and ends.
Judges on Wednesday convened to consider a petition asking it to rule on Gen Prayut's eight-year tenure.
The petition was signed by 171 MPs from the opposition bloc and forwarded to the court by the Secretariat of the House of Representatives.
The judges decided the case involves legal issues and evidence and witnesses are sufficient for the court to hand down a ruling, a source said.
On Aug 24, the court voted 5-4 to suspend Gen Prayut until it hands down its ruling on his term limit. He retains his role and duties as defence minister, however.
The suspension order followed the court's unanimous decision to accept the opposition's petition.
According to Section 158 of the constitution, the maximum term of a prime minister is eight years, but there have been disagreements over when Gen Prayut's term officially concludes.
His critics believe it should end on Aug 24 this year because the clock started on Aug 24, 2014, when Gen Prayut first became prime minister under the provisional constitution enforced after he led the coup on May 22 of that year.
Another group claims his term should end in 2027 because he was appointed PM under the 2017 charter in June 2019.
As a result, his eight-year limit would end in 2027.
Others argue the count started in April 2017 when the current charter was promulgated, meaning Gen Prayut's tenure would end in 2025.
Gen Prayut on Wednesday turned up for work at the Defence Ministry without any special engagements. No upcountry inspection trips have been scheduled, according to a source at the ministry.
The source said that before the court hands down a ruling, it will send letters to tell parties involved in the case to hear the ruling in court.
Gen Prayut will assign Maj Gen Veera Rojanavas, his legal adviser, to appear in court on his behalf on Sept 30, the source said.
Government spokesman Anucha Burapachaisri said on Wednesday Gen Prayut had been informed of the court's decision to hand down the ruling on Sept 30.
"Whichever way the court rules, the prime minister will respect it,'' the spokesman said.
"Gen Prayut has appreciated people's moral support and he is carrying out his duties as defence minister to support the government's work,'' Mr Anucha said.
"He has instructed the armed forces and agencies under the Defence Ministry to step efforts to help people affected by rain-triggered floods both in Bangkok and other provinces,'' Mr Anucha added.
Pheu Thai leader Cholnan Srikaew said the party had presented enough evidence and witnesses to the court to support the view that Gen Prayut's eight-year tenure ended on Aug 24.
If Gen Prayut's tenure ended as a result of the court's ruling, there would still be a legal dispute as to who would serve as caretaker prime minister, Dr Cholnan said.
He cited Section 168 of the constitution which stipulates that if a prime minister vacates office, he will remain in the caretaker role until a new cabinet takes office.
However, the prime minister will under no circumstances be allowed a caretaker role if he commits certain offences such as those related to budget allocations or violations of the code of ethics for political-office holders, Dr Cholnan explained.
He also said he did not believe the Constitutional Court's ruling would be a catalyst for an early House dissolution considering the government has already made arrangements to host the Asia-Pacific Economic Cooperation (Apec) summit in November.