Whether constitution writers will go along with the junta's controversial proposals such as an outsider prime minister or appointed senators will be known on Monday.
Meechai Ruchupan, chairman of the Constitution Drafting Committee (CDC), said on Thursday the draft constitution was now 80-90% complete and the proposals of the National Council for Peace and Order (NCPO) and the three bodies it appointed would be considered on March 21.
"They will be concluded on the same day," said Mr Meechai, who is also an NCPO member.
After that, the writers will review all sections thoroughly once again.
The NCPO unveiled its proposed changes to the charter draft this week. All of them involve provisional clauses, which govern how power will change hands during the five years after the constitution takes effect.
The junta claimed its proposals would help ensure a smooth transition and maintain the peace and order it had painstakingly restored.
It insisted it did not want to hold on to power but critics are not so sure.
Mr Meechai's blueprint wants senators to come from professional groups who will cross-elect among themselves. Details of which professional groups will be eligible and how the cross-election will be done will be in an organic law, which has not yet been written.
The NCPO wants the number of senators to be half that of MPs, or 250, to be screened by a committee of 8-10 people who are "independent and neutral". The senators will serve a five-year term compared to MPs' four years.
They must not be active state officials, except for six seats reserved for the chiefs of the army, navy, air force, police and the joint armed forces, as well as defence permanent secretary to "guarantee" security and order is maintained.
The senators won't be allowed to elect a PM. Their main duties are to protect the constitution, steer reforms and control the government.
"To allow senators to protect the constitution so that politicians can't distort people's will and to support a noble government, they should be able to control the administration by launching a no-confidence debate against it," the junta said in a letter to the CDC.
Mr Meechai's team will give voters only one ticket, assuming when a person votes for a candidate, he votes for the candidate's party as well.
But the junta favours two voting tickets — one for constituency MPs and the other for parties — like in previous polls. It reasoned the method would help small parties. The composition of the House will remain 350 constituency MPs and 150 party MPs.
The difference between the proposed voting method and the old system is that the NCPO wants a constituency to be bigger and represented by three MPs. Voters, however, can choose only one candidate and the top three win.
In the latest version of the draft charter, a party may propose three PM candidates, who may not necessarily be MPs, to be elected by the House.
The NCPO doesn't agree with the idea, questioning the necessity of it at this crucial time. However, this doesn't mean an outsider can't be a PM.
"Problems might emerge. A PM candidate might pull out or is disqualified. No party has a majority vote and can't agree with other parties on who should become the PM.
"If this rule is in place, even though they might want someone outside the PM candidate lists to head the government, they can't do so," the NCPO statement explained.
The selection of a PM should therefore be done freely within a timeframe but without limits on choice, it said.
Abhisit Vejjajiva, Democrat Party's leader, expressed a concern on Thursday the three-MP constituencies might not reflect people's will as voters could choose only one candidate.
"This, coupled with the proposals to scrap of three PM candidates and on appointed senators who can topple a government, indicates we're entering a political era where politicians bargain for their interests rather than let the ballots decide the country's fate.
"The problem of this country is not that a government has majority votes but rather a government abuses the votes it won. We should therefore address it at the right place, not by erasing people's will," he said.
Pheu Thai Party also issued a statement on Thursday, criticising the proposals, as well the constitution draft in general.
Having armed forces chiefs become senators by position makes a very awkward system. "They are active state officials who are supposed to follow government orders but instead they are given the power to check their boss.
"By assigning the senators to protect the constitution and steer reform, the junta turns them into the crisis panel in Mr Borwornsak [Uwanno]'s draft. It allows a bunch of appointed people to launch a censure debate against an elected government, something unheard of in democratic countries," it said.
"The proposals betray the need to keep a tight rein on the administration through their people."
A Pheu Thai member also pointed out unless a government has 376 votes or more, it can easily be toppled. The 250 senators can do so by joining hand with 125 votes of the opposition. "This means whoever becomes a PM must have the blessing of the senators."
But despite the criticisms, the junta has shown no signs of backing down, insisting the changes are necessary to maintain peace and order and will be in effect for only five years.
Asked what to do if the CDC rejects the proposals, Prime Minister Prayut Chan-o-cha said: "I'll keep sending them [proposals] until it accepts them.
"If it doesn't pass the referendum, I'll write a new one."