The junta and the cabinet have agreed to amend the 2014 interim charter so a national referendum can be held on the new draft constitution.
The decision, made after a joint meeting on Tuesday afternoon, means the general election slated for early next year in the junta's roadmap will have to be delayed by around 90 days.
Deputy PM Wissanu Krea-ngam said the polls would likely be held no later than August next year.
PM Prayut Chan-o-cha said the National Council for Peace and Order (NCPO) would not intervene in the process.
Mr Wissanu said the next step would be for the NCPO and the cabinet to propose in June an amendment to the 2014 charter to that effect and lawmakers would vote on the bill in 15 days.
He explained the prime minister could not exercise his mandate under Section 44 of the 2014 interim charter to call a referendum immediately because the powers were granted under the same constitution to be amended.
However, Mr Wissanu stressed this does not mean a referendum will definitely be held, saying the amendment aimed only at accommodating it should the need arise.
Earlier on Tuesday, Surachai Liangboonlertchai, chairman of the National Legislative Assembly (NLA), said if the NCPO and the cabinet agreed on a referendum, the government would have to take the first move by submitting a draft to amend Section 46 of the 2014 interim charter to the NLA.
Apart from stipulating a referendum, the bill must also spell out what should be done if people vote down the draft constitution, he said.
"We'll deliberate the amendment bill in 15 days in three readings. It will be a yes-no vote since the NLA has no authority to amend it.
"I agree the readings should be televised for transparency," he said.
Mr Wissanu also said after the meeting he was appointed by the prime minister to lead a team to study and propose changes to the constitution draft by June. The team will meet on May 25.
He also said three foreign experts on political law — one each from Paris, Sorbonne and Hamburg — would be invited to give speeches at the Foreign Affairs Ministry. He did not elaborate on the names or the topics they would cover.
