Thailand extended a tough security law on Tuesday for another week after opposition protest leaders called for a "historic rally" to paralyse Bangkok in a bid to force elections.

Tens of thousands of protesters remained at their open-air encampment in their trademark red shirts, calling for Prime Minister Abhisit Vejjajiva to dissolve parliament in a rally that has now entered its second week.

Their leaders, allied with toppled premier Thaksin Shinawatra, have not revealed details of their plans for the rally on Saturday and whether the demonstrators will fan out across the city as at least 65,000 of them did at the weekend.

"The cabinet sees that there is still a need to be vigilant," Abhisit told reporters, adding the law has been extended until March 30 for Bangkok and some surrounding districts.

The rally has so far been orderly.

Abhisit has refused to call early elections, which the Thaksin-allied Puea Thai Party would be well placed to win.

Puea Thai on Tuesday followed the "red shirts" in calling for parliamentary dissolution. Members planned to meet partners in Abhisit's uneasy coalition to discuss a political solution, said party chairman Chavalit Yongchaiyudh.

Key coalition partners reiterated their stance on Tuesday that they have no plan to break away from the alliance amid speculation that Puea Thai would try to bring them on board.

The Internal Security Act gives the country's powerful military-led security agency, the Internal Security Operations Command, an option to impose curfews, operate checkpoints and restricts movements if protests turn violent.

On Tuesday, the red shirts also rode on about 1,000 motorcycles around Bangkok to give out leaflets, urging city residents to join the rally.

Abhisit has not entered his office, his private home, or the parliament since March 12, instead working out of a military base which also doubles as a safe house.


Reuters