"Former members of Parliament know their constituencies and can assist in communicating with voters before the referendum on the new constitution," Matchima group leader Somsak Thepsuthin said.

The ban on political gatherings was imposed by the junta following the September coup.

Somsak said the government and the National Legislative Assembly should lift the ban because the situation had changed. Political parties can help foster dialogue and understanding of the charter drafting, he said.

After breaking away from the Thai Rak Thai Party in the wake of the September coup, Somsak and his Wang Nam Yom faction became the core of Matchima, which is in the process of developing into a political party.

Somsak welcomed attempts by two other factions to form a party.

"The arrival of new parties is a good sign for political normalisation," he said, adding he did not consider the two factions - Lam Takong and Wang Phya Nak - as political rivals.

Somsak ally Sophon Phetsawang said Matchima would monitor the charter writing.

The group has formed three panels to scrutinise social, economic and political aspects of the drafting, he said.

The group will push for no change to the 500-seat lower House made up of 400 constituency seats and 100 party-list seats.

He reminded former leader Thaksin Shinawatra to avoid involving the monarchy in politics, in a veiled reference to Thaksin's interviews to foreign news media.

"I understand why Thaksin has to speak out in order to defend himself but he should not damage the country in the process," he said.

He said the government and the Council for National Security should not force Thaksin into a corner because it could trigger reprisals.