Thai voters have gone to the polls for the first time since last year's coup to deliver a verdict on a draft constitution that the ruling junta says will pave the way for a return to democracy.
The nation's 87,000 polling stations opened at 8:00 am (0100 GMT) on Sunday for eight hours of balloting.
Election officials say they expect to announce the result late on Sunday.
Some 45 million voters are eligible, and a simple majority will be enough to approve the charter.
The junta, which ousted Thaksin Shinawatra, the twice-elected prime minister, in September last year, says the charter will pave the way for new elections later this year.
Democracy advocates argue that it rolls back reforms and could allow the military to hold sway over future governments instead.
Campaigning is tilted heavily in the government's favour, with half the country under martial law and a new law threatening prison for anyone convicted of obstructing the referendum.
If the charter fails, the generals can impose one of Thailand's 17 previous constitutions and amend it as they please.
But a rejection of the charter could reignite political tensions, delaying elections and injecting fresh uncertainty into Thailand's wobbly economy, analysts say.