Voters in Thailand are heading to the polls on Sunday for the first time since the army grabbed power in 2014. 

They are voting in a referendum on a contentious new draft constitution, which the military says will curb political corruption, bring stability and heal more than a decade of bitter political division.

Critics say the constitution - the country’s 20th since absolute monarchy was abolished in the 1930s - is intended to tighten the military's grip on democracy.

If people vote to accept the military-approved constitution, the critics say, it will cement the role of the armed forces in Thailand politics for decades, and constrain the populist forces that have arisen in recent times to challenge the country's powerful generals and their allies in the royalist establishment.

Listening Post - Thailand: the military and the media

Despite the importance of the vote, public debate has been muted.

Many have yet to see a copy of the draft constitution, while the military government has effectively banned campaigning against the document; they have arrested and detained dozens of activists and politicians in the run-up to the referendum, some of them trying to hand out leaflets urging people to vote "no".

"A public referendum is supposed to be a democratic tool, but in Thailand it has a very different look," said Al Jazeera's Wayne Hay, reporting from Bangkok.

"When opponents of the military coup tried to open centres to monitor possible cheating before the vote, they were shut down within minutes," he said.

'Rude' or 'false' discussion

In the run-up to the vote, the referendum law allowed for a 10-year prison sentence for those found guilty of "rude" or "false" discussion about the draft constitution.

Such restrictions did not apply to the "yes" vote, and the military government broadcast songs and television programmes to drum up support for a positive result in the referendum.

"Under the Referendum Act, we can't lead the public to vote no. We have already made our position clear that we will not accept this constitution." Thida Thavornseth, of the United Front for Democracy Against Dictatorship, told Al Jazeera.

One clause in the draft constitution would allow an unelected prime minister to take power in the event of a political crisis - which is exactly what happened when Thailand’s army chief Prayuth Chan-ocha, now prime minister, took power in 2014.

In the draft constitution, a fully appointed senate could block the work of elected politicians.

The 250-member senate will be appointed by the military and six seats will be reserved for security forces.

Amorn Wanichwiwatana, a member of the drafting committee of the constitution, said the planned appointed senate would act like a "steering committee" on any future governments.

"The appointed senate will guarantee that they will check and balance the power of the future government. They won't really overplay or overshadow the future government but they're acting like a steering committee I would say," he told Al Jazeera.

'No single institution which is neutral'

Polls show a large majority of Thailand's 50 million voters are undecided.

"[Thailand] is deeply divided ... worse than at any time in its history," Pavin Chachavalpongpun, a Thai academic and former diplomat, told the AFP news agency.

"There is no single institution which is neutral that is respected by all sides."

Whatever the result, the draft constitution is unlikely to be Thailand’s last - the country has seen 19 constitutions since the 1930s. With 12 successful military coups - and more than a handful of failed coup attempts in that time - it is unlikely that Thailand’s generals are going to bow out of the country’s political life any time soon.

And, as Al Jazeera's Hay noted, if the constitution is not passed, "the government says it will write another version and there will be no referendum". 

Thailand will hold a general election in 2017 even if the draft constitution does not pass the referendum, the prime minister has said.

Source: Al Jazeera and agencies