The House and the Senate of Thailand convened a joint seating on Thursday to deliberate three draft charter amendments, as rival protesters rallied near the parliament under police watch.

The three bills, proposed separately by the cabinet, the ruling Pheu Thai Party and the coalition Chart Thai Pattana Party, seek to amend the Section 291 of the constitution by establishing a Constitution Drafting Assembly (CDA). But the proposed details regarding structure and membership of the organ vary.

Under the cabinet bill, CDA will include 99 members, out of which 77 will be elected by citizens in 77 provinces. The parliament will select academics and law experts to fill the remaining positions.

The deliberation will take two days, with the Senate, the opposition and the coalition each given eight hours to debate. It is the first step to overhaul the current constitution, which was promulgated in 2007 following the military coup which toppled ex- PM Thaksin Shinawatra.

Proponents and opponents of charter amendment gathered in confrontation outside the parliament, where around 150 police were deployed to maintain security. Tul Sitthisomwong, leader of the dissenting group wearing multi-colored shirts, said they had submitted an opposing letter signed by about 30,000 people to the House.