Thousands of anti-government protesters surrounded the Thai prime minister's offices for a second day running to demand his resignation in support of former premier Thaksin Shinawatra.

Abhisit Vejjajiva told reporters he would not be swayed by the so-called "red shirts" loyal to fugitive former premier Thaksin Shinawatra who continued to encircle Government House in Bangkok early on Friday.

"Whether I resign or do not resign from my position will be determined in accordance with normal political processes," he told reporters at the parliament building, a few streets away from the rally site.

"I have no engagements there (Government House) today but if I have time I will go. (Deputy Prime Minister) Suthep (Thaugsuvan) reassured me that there is no problem and we are still going into the compound," he said.

Police said some 3000 demonstrators remained overnight after Thursday's rally, which drew an estimated 35 000 people to hear Thaksin deliver a seven-minute address by telephone.

Security remained high on Friday at the office complex, where 6000 soldiers and 3200 police stood guard as protesters vowed to continue their rally indefinitely.

Thaksin, currently living in exile to avoid a two-year jail sentence for corruption, said during his telephone address that he would call his supporters again on Friday and Saturday, indicating he wanted them to stay until then.

But British-born Abhisit said he was confident the three-month-old government would prevail, with most Thais keen for an end to the political turmoil and violence that has dogged the kingdom in recent months.

The protest is one of the biggest of several held by Thaksin loyalists since Abhisit came to power in December following a controversial court decision to dissolve the previous, pro-Thaksin government.

Thailand remains deeply polarised by the legacy of Thaksin, a charismatic billionaire who wooed the rural poor with populist schemes but was accused of graft and authoritarianism and was ousted from power in a coup in 2006.

AFP

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