Samak Sundaravej was appointed Thailand's prime minister in January
Thai Prime Minister Samak Sundaravej has said he will not resign, despite mounting anti-government protests.
Mr Samak earlier held an unexpected meeting with King Bhumibol Adulyadej, who normally stays above politics.
Thousands of protesters continue to occupy government offices in Bangkok, two provincial airports remain closed, and rail travel has been disrupted.
The protesters accuse the government of being a front for the exiled former Prime Minister, Thaksin Shinawatra.
Mr Thaksin was ousted by a military coup in 2006 and has fled the country to avoid facing trial over corruption charges.
As the political unrest continued across Thailand on Friday, Mr Samak flew to the coastal town of Hua Hin to brief King Bhumibol on the political situation.
The BBC's Jonathan Head in Bangkok says the king normally keeps out of political squabbles, but what started as a last-ditch attempt to force out the prime minister by a die-hard group of protestors, has in the space of 24 hours turned into a national crisis.
Earlier, military and government sources told the BBC that the army commander, Gen Anupong Paochinda, who until this week had stood by the prime minister, had told him he had no choice but to resign.
But in a televised ceremony honouring the royal family on Saturday, Mr Samak again reiterated his refusal to step down, saying he had "come to office in the appropriate way" when his People Power Party (PPP) was elected.
"I will never resign in response to these threats," he said.
"I came to this job under a legal mandate. I will only go if the law does not allow me to stay and not simply because someone issues threats and puts pressure on me," he added.
Later, one of the protest leaders repeated a promise that they would not to relent until Mr Samak had been forced out of office.
"The protest has already developed into a people's revolution," Sondhi Limthongkul told the Associated Press news agency.
The protests against Mr Samak's government are being led by a conservative group called the People's Alliance for Democracy (PAD).
On Tuesday, thousands of PAD supporters took to the streets of Bangkok and forced their way into government buildings.
Sept 2006: Bloodless coup by military sees PM Thaksin Shinawatra removed from office
April 2007: New military-drafted constitution approved
Dec 2007: General election won by People Power Party (PPP), seen as reincarnation of Thaksin's now banned Thai Rak Thai party
Jan 2008: Samak Sundaravej chosen as PM
Feb 2008: Thaksin returns from exile
May 2008: PAD protests against Samak begin
July 2008: Thaksin goes on trial for corruption; his wife is found guilty of fraud. By mid-August the family has fled to the UK
August 2008: PAD protests escalate
Mr Samak was initially praised for his restraint in dealing with the protests, but he suddenly found his position weakened on Friday when the police pulled back and the triumphant protest leaders were left in control of the government complex.
About 2,000 protesters then besieged the city's police headquarters, prompting the police to fire what appeared to be tear gas to disperse them.
Although the atmosphere was calmer on Saturday, the demonstrations continued outside police headquarters and thousands remained camped out at the prime minister's official compound, Government House.
For a second day, demonstrations also closed two major airports - Phuket and Krabi - in the south of the country, where protesters prevented planes from landing and taking off by occupying the runways. A third regional airport, Hat Yai, reopened on Saturday.
The PAD was originally formed in the months before the 2006 coup, to demand Mr Thaksin's resignation. It has re-emerged now that the country is being led by his former ally Mr Samak.
It has a passionate following in various parts of the country, especially Bangkok, and some powerful backers among the elite, our correspondent says.
But it has little support in most of rural Thailand, which voted strongly for Prime Minister Samak, and Mr Thaksin before him.