Thailand's Constitutional Court is expected to announce on Wednesday whether it will consider a legal challenge that could see Prime Minister Prayut Chan-O-Cha thrown out of office.

The kingdom's 2017 constitution bars the prime minister from serving more than eight years in total, and opposition parties say Prayut, who took power in a 2014 coup, has reached the limit.

If the court agrees to hear the case, Prayut could be suspended and an acting prime minister appointed.

Several hundred anti-government protesters rallied at Bangkok's Democracy Monument on Tuesday ahead of the court ruling and further demonstrations are planned.

Supporters of the 68-year-old leader argue that the clock on his rule began when the 2017 constitution was instituted, or even after the 2019 general election.

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

The former army chief came to power in a military coup that ousted Yingluck Shinawatra's democratically elected government.

He headed the junta regime for five years and continued as PM after the 2019 national elections.

The stern, blunt-speaking Prayut has found himself increasingly out of favour with voters. A recent opinion poll found two-thirds of respondents wanted him to vacate office immediately.

Under Prayut's watch, the kingdom registered its worst economic performance in 30 years and his government has also faced criticism over its handling of the pandemic.

Youth-led pro-democracy rallies 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.

On Wednesday, police had placed shipping containers on some streets near government buildings in anticipation of fresh protests.