Thai leaders have unveiled a new "road map" to a general election that could be held in July 2017.

This replaces an earlier timeframe for Thailand's return to democracy, which had elections slated by the end of this year.

It became redundant earlier this month when the military's National Reform Council rejected a Constitution drafted by the regime itself - thus resetting the process and in effect buying more time for the military to stay in power.

The military, led by then army chief Prayut Chan- o-cha, seized power in May last year after royalist street protests undermined the elected government of then Premier Yingluck Shinawatra and sabotaged a snap election, triggering a constitutional stalemate and the threat of violence.

It abolished the Constitution, banned political activity, cracked down on alleged critics of the monarchy, muzzled dissent and threatened the media.

General Prayut was named Prime Minister by a handpicked legislature in August that year.

Briefing diplomats at Thailand's Ministry of Foreign Affairs yesterday afternoon, Deputy Prime Minister Wissanu Krea-ngam said it would take 20 months to return to a general election.

But if the referendum on the new Constitution fails, the process would have to begin anew again.

A one-page handout described the stages necessary to create the new Constitution - Thailand has had 19 Constitutions since changing from absolute to constitutional monarchy in 1932 - and hold a general election.

These included setting up two new bodies - a Constitutional Reform Driving Council and a 200-person National Reform Steering Assembly.

The new council would draft the document, which would then be put to a referendum, followed by a long process of drafting, passing and vetting of organic laws, and the general election itself.

It is possible to make the period shorter but not by much, Mr Wissanu said.

Earlier in the day, the notoriously blunt-speaking Premier, Gen Prayut, who appears to be growing increasingly impatient with criticism that he is attempting to cling to power, told journalists that "the next general election could be organised around July 2017".

The rejection of the draft Constitution on Sept 6 was widely seen as a ploy by the regime itself.

Political science professor Thitinan Pongsudhirak, writing in the Bangkok Post newspaper last Saturday, said "the generals have been given relative slack by Thai society".

But he cautioned that the "implicit bargain... has an expiry date that has been accelerated by the charter debacle".

"Whatever trust and benefit of the doubt the Thai people were willing to allow have now been eroded," he wrote.