BANGKOK - Thai voters flock to polling stations across the country on Sunday for the country's first general election since the 2014 coup.

Eligible voters have been lining up at polling station since 6:00 am local time. Prime Minister Prayut Chan-o-cha cast his ballot at a station in Bangkok at about 8:30 am local time.

The prime minister asked voters to use their rights properly to bring about unity and better development of the country.

High ranking government officials and leaders of political parties also showed up at polling stations in the morning.

Deputy Prime Minister Prawit Wongsuwan reiterated that security of the country is the top priority of the government, ruling out political unrest during election.

The vote will be held from 8:00 am to 5:00 pm local time on Sunday. More than 51 million people are registered as eligible voters.

There are more than 90,000 polling stations across the country. The Election Commission expected that at least 80 percent of voters will cast their ballots.

Unofficial results will be unveiled about three hours after the polling stations close. Official results will be announced before May 9.

Thai King Maha Vajiralongkorn made a call for unity and happiness just 12 hours before the vote.

In the election, voters will choose 350 senators in the lower house. The new constitution allows parliament's upper house, the 250-seat Senate, to vote with the 500-seat lower house to choose the prime minister.

Pro-military parties would probably need 126 seats in the lower House of Representatives to win a majority in a combined vote. Opposition parties would need 376 seats.