Thai referendum voters appear to have backed a draft constitution written by an army-appointed committee.
Thailand’s election commission says that with 91% of the votes counted, 61% have voted in favour.
The military threw out the old constitution when it took power in 2014, after months of political instability and sporadic violence.
Supporters of the new document say it will restore stability, but critics say it will entrench military control.
Voters also appear to have supported a second measure on the ballot, which proposes that the appointed senate should be involved in selecting a prime minister.
The election commission says 58% of the votes counted so far are in favour of this.
The final result is expected in the next few hours.
Campaigning against the draft had been banned and dozens of people have been detained. Thailand’s biggest political parties rejected the constitution.
After casting his ballot at a polling station in Bangkok, Prime Minister Prayuth Chan-ocha said: “Come out [to vote] because today is important for the future of the country.
“This is your duty and this is part of democracy, of an internationally-recognised process.”
About 200,000 police officers were deployed to maintain order and there were no reports of protests.