Anti-government protesters began gathering in Bangkok on Friday for what they promise will be a million-man march in coming days to paralyze Thailand's capital and force the government to call elections.

About 40,000 soldiers and police fanned out across the city as several thousand red-shirted supporters of deposed premier Thaksin Shinawatra began gathering in one of the biggest challenges yet to Prime Minister Abhisit Vejjajiva.

But the political turbulence has failed to shatter confidence in Thailand's financial markets. Many investors and political analysts doubt even violent protests will derail the government, which is backed by the military's top brass and the urban elite.

In a reflection of this, Thai stocks have surged 75 percent in the past 12 months on nearly $2 billion of foreign fund inflows, though they were a touch weaker on Friday on some disquiet among local retail investors.

In five major areas of Bangkok, protesters gathered under searing afternoon sun to listen to speeches by leaders of their movement, the United Front For Democracy Against Dictatorship (UDD), standing on trucks-turned-makeshift stages.

We are calling for the return of power to the people. Let them decide the fate of this country, one red shirt leader, Veera Muksikapong, told cheering supporters.

Economists caution that possible unrest could hurt some businesses and sap consumer confidence in Southeast Asia's second-biggest economy, possibly forcing the central bank to delay an expected rise in interest rates from record lows.

But most expect the rising trend in Thai stocks, among the cheapest in Asia, to remain intact, noting that red shirt protests last April that sparked Thailand's worse political violence in 17 years failed to unseat the government.

Foreign investors are more focused more on a swift, export-led economic rebound in Southeast Asia's emerging markets, and have snapped up about $500 million of Thai stocks since January, with most of the buying in recent weeks.

Like the UDD's 'last stand' in April 2009, the 'million-man march' may prove to be nothing of the kind and the stability of this regime offers encouragement to investors, said Timothy Powdrill, a political risk analyst at consultancy Riskline ApS.

INTRACTABLE CRISIS

The protesters will disperse later on Friday before regrouping on Sunday with the red shirts vowing to bring hundreds of thousands from the provinces into Bangkok's streets -- a scale almost unprecedented in recent years. Organisers say the rally will last at least seven days.

Many businesses and schools were shut in the capital while some companies allowed staff to work from home.

Armed guards stood at many banks and state buildings after government warnings of potential sabotage, including bombings.

The protests add a new strain to a seemingly intractable political conflict pitting the military, the urban elite and royalists, who wear the revered king's traditional color of yellow at protests, against the mainly rural supporters of Thaksin, who say they are disenfranchised and wear red.

The protesters say the Oxford-educated Abhisit came to power illegitimately by forming a parliamentary coalition with the help of the military that toppled Thaksin in a 2006 bloodless coup on charges of massive corruption and disloyalty to the monarch.

The red shirts chafe at what they say is an unelected elite preventing allies of twice-elected Thaksin from returning to power through a vote. Adding to their anger, Thailand's top court last month seized $1.4 billion of Thaksin's assets, saying they were accrued through abuse of power.

Protesters marched to a military base where Abhisit held a security meeting, police headquarters and a government television station. Thousands chanted: Elites get out.

Few expect a million protesters, but the prospect of even tens of thousands flooding the streets has rattled nerves in the city of 15 million people.

There are all sorts of rumors going around about how it may turn violent so it is best to close, then wait and see, said Puangthong Limjitikul, an open-air restaurant owner in Bangkok.

Protesters accuse authorities of trying to fan the fears, but the government insists the threat of violence is real.

I will not respond to threats, Abhsiti told reporters.

Government House, which includes Abhisit's office, has been cordoned off. Authorities have closed several other roads to prevent protesters from besieging government buildings.

In 2008, a rival protest group sought to topple a Thaksin-allied government by seizing Government House for three months and shutting the country's international airport for eight days. The UDD insist they would not use the same tactics.

Thailand