But many also fear the ballot could trigger a new era of upheaval if the results are not accepted by rival protesters or the coup-prone army.

Television stations reported long lines at polling stations across the country as registered voters waited to choose among 42 parties contesting the ballot. Security was tight, with around 170,000 police deployed nationwide to protect voting booths.

While the poll itself is a race between ruling Democrats led by Prime Minister Abhisit Vejjajiva and opposition leader Yingluck Shinawatra's Pheu Thai party, it has come to be viewed as a referendum on the divisive legacy of former premier Thaksin Shinawatra, Yingluck's exiled elder brother.

Thailand "is at a crossroads," said Siripan Nogsuan Sawasdee, a political scientist at Bangkok's Chulalongkorn University. If the results are not respected, "we'll be back to ground zero — more protests, more violence."

AP