Thailand's military government has held reconciliation talks with the leaders of the Puea Thai party it toppled from power nearly a year ago, along with other politicians, academics and student activists.

The talks, held at the site of the May 2014 coup staged by the army, come as Thailand debates a draft constitution that the junta says will help heal the country's deep divisions, but which parties from both sides of the political spectrum have criticised as undemocratic.

Members of the conservative Democrat Party also attended the meeting. Some of the participants called for the draft charter to be put to a referendum.

Thailand needs to reach a constitution acceptable to all, said Jatuporn Prompan, a leader of the opposition red shirt movement and a former lawmaker of Puea Thai.

"If the public does not agree, we have to amend the constitution," Mr Jatuporn, who attended the meeting, said. "Even if it means wasting another year or two, it is better than moving forward to where problems will be waiting."

Thailand's military rulers have said a general election will be held in 2016 but warned a return to democracy could be pushed back if the country held a referendum.

Critics say a provision in the charter for proportional representation would lead to weak coalition governments.

They say the charter is an attempt to ensure limited powers for any future government allied to ousted former Prime Minister Thaksin Shinawatra.

The constitution also includes a curb on populist-style policies, such as those favoured by Thaksin and his sister Yingluck, who was the leader of Puea Thai.

Ms Yingluck's administration was toppled in the 2014 coup, while Mr Thaksin was the victim of another coup in 2006.

Thailand has suffered nearly a decade of political turmoil as Mr Thaksin and his allies have vied for power with the traditional Bangkok elite threatened by his meteoric rise.

Mr Thaksin lives abroad to avoid a jail sentence handed down for corruption in 2008.

Since taking power, the junta has stifled dissent by detaining politicians and activists for "attitude adjustments", targeting mostly supporters of the government it ousted.

The junta has been criticised for lifting martial law and replacing it with a security provision in the interim constitution, known as section 44, that gives sweeping powers to the military.

Prime Minister Prayuth Chan-ocha, who, as army chief, led the May coup, said he would not use the security clause to force reconciliation.