Thousands of anti-government protesters headed for Bangkok from rural Thailand on Saturday for what they call a million-man march, aiming to paralyze the city and topple a government they say is a front for unelected elites.

The red-shirted supporters of ex-premier Thaksin Shinawatra, ousted in a coup in 2006, will rally in Bangkok from Sunday and say they will stay for at least seven days, aiming to force Prime Minister Abhisit Vejjajiva to call an election that Thaksin's allies would be well placed to win.

Some 600,000 to 700,000 'red shirts' are on their way to Bangkok and, together with those already in town, we will have more than a million people, Woravat Auapinyakul, a member of parliament for the pro-Thaksin Puea Thai Party, told reporters.

Investors are worried about violence, and about the government being distracted when it should be concentrating on nurturing the economy as it recovers from a brief recession.

But Thailand is still benefiting from investment funds flowing into Southeast Asia and foreigners have snapped up $500 million of Thai stocks so far this year, much of it this month. The stock market rose 1 percent on Friday. About 40,000 soldiers and police were mobilised in the capital from Friday, when several thousand red shirts gathered at several points for warm-up events ahead of the main rally.

On Saturday, a Reuters photographer counted thousands of pickup trucks streaming into Bangkok along a main road from Thaksin's strongholds in the north and northeast of the country, carrying red-shirted supporters waving flags. Police stopped them and searched for weapons, then let them proceed.

Around 3,000 protesters gathered on Ratchadamnoen Road, a thoroughfare in central Bangkok leading to the bridge that will be the main site for the rally on Sunday.

We want democracy and justice for the society. We want the government to dissolve parliament and return power to the people, said Nisarat Laokonkam from Nan in the north, adding she quit her job as a teacher to work for the red shirts.

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

We have stepped up security at key areas which may become targets, said army spokesman Colonel Sansern Kaewkamnerd, listing court buildings, the homes of prominent people and Bangkok's main Suvarnabhumi airport as possible targets.

NUMBERS CRUCIAL

Roberto Herrera-Lim, an analyst at Eurasia Group, said the red shirts recognized violence would be counter-productive and were now intent on building up public support for what they present as a pro-democracy movement.

Whether the 'red shirts' will accomplish anything at all depends on the numbers that they can muster, he said.

The conventional wisdom in Bangkok is that for the rallies to have a visible and near-term effect on the viability of the current coalition government, the opposition will have to bring at least a couple of hundred thousand protesters into Bangkok by Sunday, Herrera-Lim said in a note to clients.

In 2008, a rival group sought to topple a Thaksin-allied government by seizing Government House for three months and shutting Bangkok's two main airports for eight days, damaging the tourist sector and dealing a blow to investor confidence.

The United Front For Democracy Against Dictatorship (UDD) movement insist they will not use the same tactics.

So far, the situation remains normal, Sansern said. We believe the protesters will be peaceful but we have to make sure there are no outside instigators.

The protests add a new chapter 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 Thaksin supporters.

The protesters say the Oxford-educated Abhisit came to power illegitimately, heading a coalition cobbled together by the military after a pro-Thaksin party leading the previous coalition government was dissolved by the courts.

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 seized $1.4 billion of his assets last month, saying it was accrued through abuse of power.

Thaksin fled Thailand in 2008 to escape a two-year sentence for graft. Woravat said he was in Dubai, now his main base, but

would be flying to Europe soon to meet up with his daughters.

Abhisit spent the night in a Bangkok military barracks, which is his center of operations for the duration of the rally.

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

Protesters accuse the authorities of scaremongering with talk of possible bombings and arson, but the government insists the threat of violence is real.

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

(Additional reporting by Orathai Sriring, Pracha Hariraksapitak. Ambika Ahuja, Martin Petty, Sukree Sukplang and Papitchaya Boonngok; Writing by Alan Raybould; Editing by Paul Tait)

Thailand