By Kittipong Soonprasert

BANGKOK - Thousands of anti-government protesters stopped Thai Prime Minister Abhisit Vejjajiva from entering his office on Friday and vowed to continue their siege until he stepped down.

The campaign, that began on Thursday, does not pose a serious threat to Abhisit's three-month-old government, analysts say, but may distract policy makers from reviving an economy hit by the global downturn and Thailand's long-running political crisis.

'We will stay here as long as it takes to get Abhisit out of office,' Jatuporn Prompan, a UDD leader and member of parliament for the pro-Thaksin Puea Thai opposition party, told Reuters.

Abhisit, who easily survived a no-confidence vote in Parliament last weekend, and his ministers avoided the Government House compound to minimise the risk of clashes between police and the red-shirted demonstrators.

The compound was occupied for three months last year by the anti-Thaksin People's Alliance for Democracy (PAD), which also seized Bangkok's main airport for more than week in a bid to force out a government loyal to the former premier.

Senior PAD leaders have said they will report to the police on Monday to face charges of public disorder in connection with last year's protests.

Thaksin, who lives in exile after being convicted on conflict of interest charges by a Thai court last year, was due to address the 30,000-strong UDD rally by video link later on Friday.

In past speeches, Thaksin has attacked the government's economic stimulus measures as too little too late, and vowed to fight for what he has called "real democracy" in Thailand.

Financial markets have paid little attention to the peaceful rally, with the Thai stock market extending Thursday's gain after better economic news from the United States and a positive response to the latest US efforts to repair the banking system.

'Although "red-shirt" protests are stirring tensions, we believe the political situation will continue to be relatively stable, as was indicated in the government easily surviving a recent no-confidence motion,' top broker Kim Eng Securities said in a note to clients.

Nevertheless, the street campaign could distract ministers as they strive to mitigate the effects of a global economic slump that has hit Thailand's key export and tourist sectors.

The finance ministry warned this week that the economy could shrink by as much as 3 per cent this year and said the jobless rate could jump to 3.8 per cent, representing about 1.4 million people, from 1.4 per cent at the end of last year.

More than two years after Thaksin was removed, the political impasse between Bangkok's royalist and business elite, who accused Thaksin and his allies of corruption and abuse of power, and rural voters who loved his populist policies, shows no sign of abating.