The Senate is scheduled to vote tomorrow on a controversial proposal to hold a referendum that could pave the way for a rewrite of the charter.
Senate was originally supposed to vote in November but it was postponed when senators decided to form a committee to study the motion before deciding whether to second it.
On Nov 3, the House voted to pass the opposition-sponsored motion and forwarded it to the Senate for a vote.
The motion calls on the government to hold a referendum on whether a new charter should be drawn up to replace the current charter.
It also suggests that the referendum be arranged on the same day as the next general election, which is tentatively set for May 7 by the Election Commission.
Before the vote tomorrow, senators will read a report prepared by the panel headed by Sen Somchai Sawaengkarn.
The executive summary says the committee disagrees with the rewrite of the entire charter out of concern it may lead to structural changes of state agencies and affect the duty and authority of public independent agencies, civil liberties, national identity and collective values.
It says charter amendments to address problematic parts can be carried out without the need to draw up a new one.
Claims that the current constitution is a product of the one in 2019 do not justify the call for a rewrite, it says.
It said the question to be put up for the referendum does not define the scope of the charter rewrite and this may affect the country's governing system where Thailand is a single, indivisible kingdom under a constitutional monarchy.
The panel points said the motion may run counter to the charter, which grants amendment powers to parliament.
Rewriting the entire constitution by a drafting assembly may be in violation of the charter, it says.
It says rewriting a new charter and holding a referendum are costly. There are likely to be two referenda, one before and another after a charter amendment which will cost about 7 billion baht, plus at least 100 million baht to subsidise the drafting process, it says.
Jullapan Amornwiwat, Pheu Thai MP for Chiang Mai who proposed the motion, said yesterday he is not surprised by the report as MPs and senators do not see eye to eye on charter charges.
"There is only one charter amendment that is approved by parliament. That concerns the elections of MPs because those in power gave it a nod and government coalition partners wanted it," he said, adding that if Senate shoots down the motion, that is the end of the story.