Three coalition parties and the opposition are making a unified stand to strip the Senate of its power to take part in selecting a premier by seeking to alter the charter through 14 amendment drafts.
The Bhumjaithai, Democrat and Chartthaipattana parties along with the opposition bloc on Wednesday filed 14 drafts between them seeking to rectify multiple sections in the constitution.
Between them, they have outlined many different key areas in the charter they want changed.
However, they are united in pressing for an amendment to Section 272 to keep the Senate from joining MPs in electing a prime minister.
Both the opposition and coalition parties submitted the 14 draft amendments to Parliament President Chuan Leekpai on Wednesday.
The number of drafts filed corresponds to the number of issues which the parties have targeted for the constitution rewrite.
Chinnaworn Bunyakiat, deputy chief government whip and Democrat Party MP, said that apart from stripping the Senate of its prime ministerial voting powers, three parties were looking to improve the 20-year national strategy plan and push for better protection of civil liberties and consumer rights.
Other issues included restoring the two-ballot electoral method, restricting the choice of prime ministerial candidates to those nominated by parties or MPs, reverting back to requiring the backing of two-fifths of parliament to launch a charter amendment bid, and better decentralisation of power.
Mr Chinnaworn said the coalition parties would support opposition drafts which they find agreeable.
Mr Chuan said on Tuesday that parliament will convene on June 22-24.
On June 22, it will deliberate a backlog of legislation, including the referendum bill.
The following day, it will proceed with charter amendment motions submitted by both the government coalition parties and opposition bloc.
Mr Chinnaworn said a House debate on the draft amendments will precede a vote to admit them in the first reading. During the debate, parties sponsoring each draft will explain the reasons for their proposed amendments.
After that, the drafts will be up for scrutiny, a process spanning up to 45 days, before they are put to a third and final reading and vote.
Also, Supachai Jaisamut, a Bhumjaithai list MP, said his party wanted the charter to specify the state's role in providing a universal minimum income guarantee for citizens.
The 20-year national strategy must be revised to keep abreast with the changing world while the Senate must be made to relinquish its prime ministerial selection power, he added.
Meanwhile, opposition leader Sompong Amornvivat led the opposition parties as they tabled their five amendment drafts to Mr Chuan in parliament on Wednesday.
The opposition was represented by the Pheu Thai, Move Forward and Seri Ruam Thai parties.
Among items in the five drafts the opposition seeks to rewrite is Section 256 which involves replacing the current charter.