Thailand's prime minister launched Tuesday a committee to look at amending the military-drafted constitution, but ruled out any changes to contentious sections related to the monarchy.

Premier Srettha Thavisin's new government came into office in August after months of political wrangling, having promised constitutional reform in the run-up to May's general election.

The current charter was drafted in 2017 following a 2014 military coup, and heavily weights power towards unelected officials and the armed forces.

Srettha's Pheu Thai party had pledged to hold a referendum on changing the constitution, telling voters it had been used to extend the rule of the then-junta.

On Tuesday, Srettha appointed a 35-member committee to conduct a feasibility study on holding a referendum to amend the constitution.

"We have a timeframe of three to four months, or at least before the new year, for a conclusion on the referendum," Deputy Prime Minister Phumtham Wechayachai said.

The committee will contain representatives from the government and opposition, as well as academics, political activists and legal experts, he told a press conference.

Phumtham said the process could take more than three years, but that it would be open to public discussion.

He said the cabinet will approve and submit the committee's recommendations to the Election Commission before a referendum.

But the new charter will not change anything related to the monarchy.

"We will not touch Chapter I and Chapter II including the Royal prerogatives in other articles," Phumtham said.

King Maha Vajiralongkorn and his close family are protected by some of the world's toughest lese-majeste laws, with offences punishable by up to 15 years in prison.

Youth-led street protests in 2020 made unprecedented calls for changes to the king's power and privileges.

The committee is expected to hold its first meeting next week.