People across Thailand are going to the polls in a referendum on a new constitution, written by a military-appointed committee.
The military threw out the old constitution when it took power in 2014, after months of political instability and sporadic violence.
It says that if approved, the constitution will be a major step towards returning to full democracy.
But opponents call the vote unfair as campaigning has been restricted.
The Referendum Act, brought in to govern the referendum process, criminalises ‘anyone who disseminates text, pictures or sounds that are inconsistent with the truth’.
Rights groups have said that new laws ‘restrict expression and access to information about the draft constitution’.
At least 17 people have been charged with violating the Referendum Act and face a maximum sentence of 10 years in prison.
Supachai Somcharoen, chairman of Election Commission of Thailand, displays a voting paper during a Thai constitution referendum promotional event organized by the Election Commission of Thailand, on August 4, 2016 in Bangkok, Thailand.Image copyrightGETTY IMAGES
What are Thais voting on?
The 40 million voters will answer yes or no to the question: Do you accept the draft constitution?
If the majority of voters say yes, the draft becomes the constitution and the military is given legitimacy in the run up to an election which Prime Minister Prayuth Chan-ocha - who led the 2014 coup - has promised will happen next year.
If the constitution does not pass, what will happen is uncertain, but the military government will remain in control.
Voters will also be asked: Should the upper house of parliament be permitted to join the lower house in selecting a prime minister?
What are the key changes in the draft?
Civil servants and military school students attend a Thai constitution referendum promotional event organized by the Election Commission of Thailand, on August 4, 2016 in Bangkok, Thailand.
The military argues that it is corrupt politicians that are to blame for the last decade of instability and divisive politics.
Made public in March, the draft proposes making it very difficult for a single political party to hold a majority.
One of the most controversial clauses calls for the 250-seat senate to be fully appointed by the military government.
Before the coup, just over half of the upper house seats were directly elected and the rest were appointed.
The change means military-appointed lawmakers would have a majority over elected leaders in the National Assembly of Thailand.
Critics say the amendments greatly enhance the power of the military, and ensure it will have a grip over Thai politics for at least five more years.
Why is this happening?
Thai election authorities on Wednesday filed their first charge under a law banning campaigning and debate before a referendum on a controversial new constitution, as the junta tightens its grip on free speech.
Thailand has had a decade of fractured politics and instability that have sometimes spilled over into violence on the streets.
In this time, parties linked to former Prime Minister Thaksin Shinawatra have won every election, but their governments have been ousted either by court rulings or military coups.
Mr Shinawatra fled into self-imposed exile in 2006 to escape corruption charges for which he was later convicted in absentia.
His sister, Yingluck Shinawatra, became prime minister in 2011 but was ousted by a court order, also on corruption charges, days before the military took power.