Constitution writers and whips for the National Reform Council (NRC) agreed on Wednesday that the new charter draft should be put to a referendum before it is promulgated.
The Constitution Drafting Committee (CDC) unanimously voted in favour of the referendum at its extraordinary meeting Wednesday.
The proposal will be submitted to Gen Prayut Chan-o-cha in his capacity as prime minister and chief of the National Council for Peace and Order later in the day, said Gen Lertrat Rattanavanich, a CDC adviser and spokesman.
Gen Prayut has the authority to amend the interim charter so the referendum can be held, he said.
"We agreed the new charter should be put to a referendum so people can take part in it. It will also be in line with the 2007 charter. Besides, since future amendment of the new constitution will require a referendum, the charter itself should get the same treatment," he said.
Legal measures to pave the way for the referendum should be completed in July. The referendum can be held in 90 days after the NRC endorses the draft to allow time for people to study the content. The most likely timeframe is therefore the end of this year.
The CDC has not said what voters will be asked in the referendum. For the 2007 charter, the referendum asked voters whether to accept the constitution draft or to let the 2006 coupmakers pick any of the past 17 constitutions in its place. This drew cricitism that this was not the way to hold a referendum because voters did not know what would happen if they voted "no".
Earlier, Paibul Nititawan, a CDC member, proposed that a referendum should be held, but not on the new charter.
He floated the idea that voters be asked whether national reforms should continue over the next two years before an election can be held.
He reasoned the extra time was needed to complete the work in key areas. What was left unsaid though is that Gen Prayut would continue to be the prime minister during the transition and the roadmap he had announced would have to be changed.
Mr Paibul's proposal won staunch support from dozens of NRC members, including Wanchai Sornsiri.
"There's no rush for Thailand to have an election. Actually, such a referendum might not be needed because reform is what a majority of people need anyway. Besides, when the NCPO seized power, it did not ask for people's opinions," said Mr Wanchai said on Tuesday.
"If an election is held when reforms have yet to be completed, there might be criticism this coup is half-done and achieves nothing. It will be a waste," he added.
However, Mr Wanchai personally thought the NRC should not continue to work for the next two years since it could face criticism of trying to perpetuate its power.
"The NCPO and the cabinet can do the job or set up a new body to steer reforms. Such a body need not be big, maybe 50-100 members. It could do the job for 1-2 years," he said.