BANGKOK, Thailand -- Thailand's Constitutional Court said Wednesday it will rule on September 30 whether suspended prime minister Prayut Chan-O-Cha should be thrown out of office permanently.

The former army chief, who came to power in a 2014 military coup, was suspended last month while the court examined a legal challenge arguing he has reached his term limit as premier.

Under the 2017 Thai constitution, a prime minister cannot serve more than eight years in office, but there are question marks over when Prayut's term began.

The court said in a statement that it will issue its verdict on September 30 at 3pm (0800 GMT).

"The Constitutional Court deliberates that the case is a legal issue and there is sufficient evidence to rule," the statement said.

Prayut's deputy Prawit Wongsuwan has taken over as caretaker prime minister, while Prayut continues to serve as defence minister.

Prayut launched the coup that ousted Yingluck Shinawatra's democratically elected government, and led a junta regime before retaining the prime ministerial post after elections in 2019.

Supporters of the 68-year-old leader argue the clock on his term began when the 2017 constitution came into law, or even after the 2019 general election.

If the court agrees, Prayut could technically continue to serve until 2025 or 2027 -- if he wins a general election due by March.

But Prayut is increasingly out of favour with voters and under his watch the kingdom registered its worst economic performance in three decades.

Student-led pro-democracy protests in Bangkok in 2020 attracted tens of thousands of people at their peak and a key demand of the movement was for Prayut to resign.

Thailand is under pressure to end the uncertainty over its leadership before world leaders arrive in Bangkok for an Asia-Pacific Economic Cooperation (APEC) summit in November.