With less than 48 hours left before the fate of the draft constitution is known, Prime Minister Prayut Chan-o-cha has called on National Reform Council (NRC) members to exercise fair judgement before they vote on it.
Gen Prayut reassured the public in his weekly speech on Friday that neither the government nor the National Council for Peace and Order (NCPO) had intervened to suggest the direction of the vote.
But he urged all NRC members to "study the draft carefully" as it was written to serve the people and set the tone for reforms to continue. The charter writers, he said, had no intention to draft a constitution to please political parties or the NCPO.
"People should be the centre, not political parties, not any one group and not the NCPO," he said on his Returning Happiness to Thai People programme.
"If [the charter is] passed, we should be confident that national reforms will take place without conflicts," he continued. "If it is rejected, we should go over the draft and amend problematic provisions."
"But if the only reason behind the rejection is because it is perceived as undemocratic, I think that would be unfair to the people."
In any case, Gen Prayut said the decision of the NRC should be "logically made" on Sunday.
There are 247 NRC members and at least 124 votes are needed to pass the draft. It will be a straight yes-no vote with no further changes allowed.
The Constitution Drafting Committee (CDC) has 36 members in total and 21 of them hold seats on the NRC. Critics have said it would be a conflict of interest to allow the drafters to vote.
However, Deputy Prime Minister Wissanu Krea-ngam said recently that there was no law or rule that prevented the charter writers from voting on the document they had written.
Even after being pared back from 315 sections to 285, the draft charter, at 124 pages, is one of the longest in the world. (The constitution of India, at 117,000 words or about twice as many as the Thai draft, is the longest.)
The draft has attracted considerable criticism, not only for its bulk but also for the last-minute addition of a "crisis panel" that would be able to take over from an elected government if such action is deemed necessary.
Other contentious features include a provision that allows an "outsider" or non-MP prime minister, and a Senate dominated by appointed members.
CDC chairman Borwornsak Uwanno and Mr Wissanu defended the proposed crisis panel, saying it would not be formed to steer a government after new elections. The committee, which would include all military chiefs and other senior figures, would help solve national problems and prevent future conflicts, they say.
Mr Borwornsak also said the charter was intended to cater to the needs of all stakeholders across the political spectrum, which is one reason it is so bulky.
Both the Pheu Thai and Democrat parties oppose the draft on the grounds that it runs counter to democratic principles.
But former protest leader Suthep Thaugsuban has thrown his support behind the draft, saying it would help move the country forward through reforms. The former Democrat power broker now leads the Muan Maha Pracha Chon for Reforms Foundation.
Many provincial NRC members are known to be opposed to the draft, saying they would have trouble explaining the "undemocratic" parts to people in their regions. The vote is expected to be very close.
The NRC will start its meeting at 10am on Sunday and the vote on the draft is expected by noon. All members will be asked one by one whether they accept or reject the draft, NRC whip Alongkorn Polabutr said on Friday.
Mr Alongkorn acknowledged that members were being lobbied by their colleagues to vote one way or the other, saying it was normal practice in any kind of political body.
If the NRC endorses the document, a national referendum will be held, probably no later than January. If it rejects the draft, the junta will appoint a new CDC to draft another charter within 180 days.
Regardless of the outcome, the NRC will be dissolved after the vote.