Polls opened in Thailand on Sunday in a general election defined by a three-way battle between the country's conservative, progressive and populist camps, with no single party expected to secure a clear majority, prolonging the spectre of political instability.

Prime Minister Anutin Charnvirakul set the stage for the snap election in mid-December, amid a raging border conflict between Thailand and Cambodia, in what analysts said was a move timed by the conservative leader to cash in on surging nationalism.

At that point, he had been in power for less than 100 days, taking over after the ouster of premier Paetongtarn Shinawatra of the populist Pheu Thai party over the Cambodian crisis.

Pheu Thai, backed by the billionaire former prime minister Thaksin Shinawatra, who himself went to jail just days after his daughter's removal, is down but not out, according to surveys.

But it is the progressive People's Party, with its message of structural change and reforms to Southeast Asia's second-largest economy, that has ⁠consistently led opinion polls during the campaign season.

"This election is about whether Thailand will get out of its rut, whether Thailand will break out of its political instability and economic doldrums that have persisted," said Thitinan Pongsudhirak, a political scientist at Bangkok's Chulalongkorn University.

"My preliminary conclusion, I'm afraid to say, is that it will not break out."

Although it has taken the fight to Anutin's ruling Bhumjaithai Party and Pheu Thai, People's Party may not have enough support to win a parliamentary majority on its own - raising the risk of repeating its predecessor's fate.

Move Forward, the forerunner of the People's Party, won the last election in 2023 only to be blocked from forming a government by a military-appointed Senate and conservative lawmakers, opening the door for Pheu Thai to take over.

This long-standing tussle between the powerful royalist-conservative establishment and popular democratic movements has created prolonged periods of uncertainty, punctuated by street protests, bouts of violence and military coups.

Under Thai law, out of the 500 seats available in Thailand's House of Representatives, 400 seats will be elected in constituencies across the country, with the remaining 100 allocated to political parties on a proportional basis.

Meanwhile, the outcome of the constitutional referendum will determine whether parliament will initiate the constitutional amendment process. (Reuters/Xinhua)