About 80,000 red-shirted supporters of former prime minister Thaksin Shinawatra, ousted in a military coup in 2006, arrived in trucks, cars and motorbikes from rural provinces over the weekend, carrying red flags as loudspeakers blared music about democracy and freedom.

Tens of thousands more protesters were expected by March 14 evening.

Investors worry that any violence could derail a nascent recovery in Southeast Asia's second-biggest economy.

Protest leaders insist the rally will be peaceful even if it lasts for days. They plan to maintain pressure on Prime Minister Abhisit Vejjajiva to dissolve parliament and call an election Thaksin's allies would be well-placed to win.

If that is not met, they will march throughout Bangkok, said a protest leader, Nattawut Saikua, raising the prospect of paralysing many of the capital's already-congested streets.

Reuters