The charter rewrite debate has started in parliament on a stormy note, with the Democrats accusing the government of pursuing vested interests as the first three amendment bills were accepted by the House.
The Democrats said the rewrite bid was an attempt to clear the way for ousted former prime minister Thaksin Shinawatra to return home.
Opposition party MPs also warned they would oppose any efforts to amend provisions in the constitution relating to the monarchy.
Parliament yesterday voted 341 to 181 to proceed with consideration of three bills after two hours of stormy debate.
The amendment proposals seek to change Section 291 of the constitution to create a constitution drafting assembly (CDA) to work out proposed amendments to the charter.
The bills were submitted by Pheu Thai MPs, Chatthaipattana MPs and the cabinet.
The Democrats wanted debate postponed until another three bills proposed by the public and civic groups could be submitted. The party was unsuccessful.
Democrat leader Abhisit Vejjajiva said the Pheu Thai-led government and its allies had made it clear the proposed charter amendments were aimed at bringing Thaksin back home.
Democrat list MP Jurin Laksanavisit said the government's proposed amendments were driven by a hidden agenda aimed at clearing Thaksin's name.
Democrat list MP Banyat Bantadtan said if the charter changes were allowed to take place, nobody could guarantee provisions relating to the monarchy would remain intact.
He said his party opposes any efforts to amend such provisions, particularly Section 77 which requires the state to protect and uphold the institution of the monarchy.
Deputy Prime Minister Chalerm Yubamrung said the charter rewrite drive was one of Pheu Thai's election promises which the government must fulfil.
Mr Chalerm said the government will table a bill on national reconciliation to parliament to pave the way for Thaksin to return to Thailand, although political circumstances will also be taken into account.