Bangkok, May 14 (IANS): Polling is underway for Thailand's general election on Sunday, and Prime Minister Prayut Chan-o-cha has cast his ballot.

He called on Thai people to vote in the election to exercise their right.

The polls started at 8:00 a.m. (0100 GMT) and will continue until 5:00 p.m. local time (1000 GMT) on Sunday. More than 52 million Thai citizens are eligible to vote in the election, Xinhua news agency reported.

In the run-up to the polling day, parties in Prayut's government were trailing behind in the opinion polls behind major opposition parties, including the Pheu Thai Party links to former PM Thaksin Shinawatra and the Move Forward Party which has been popular among young voters.

Under the two-ballot system with one vote for the 400 constituency members of parliament (MPs) and another for their preferred party vying for the 100 party-list MPs, voters will elect a total of 500 members to the House of Representatives, or lower house of the parliament.

The Election Commission is expected to announce an unofficial result late Sunday.