Tens of thousands of protesters have held a rally in the Thai capital, Bangkok, demanding the resignation of Prime Minister Thaksin Shinawatra.
Protesters say Thaksin Shinawatra. is "robbing" Thailand
They voiced their anger over a $1.9bn business deal involving Mr Thaksin's family, accusing of him of corruption.
Mr Thaksin - who says he has done nothing wrong - has insisted he will only resign if asked by the king.
In his weekly radio address, he said he was confident that most Thais wanted him to remain in office.
At least 15,000 people gathered in Bangkok's Royal Plaza, near the parliament building and the royal palace, Thai officials said.
Chanting "Thaksin get out", many protesters wore armbands that read "Salvage the nation".
Mr Thaksin says the majority of Thai voters supports him
"We come here to oust Thaksin," Wichan Saensan, a teacher, was quoted as saying by the Associated Press news agency.
"We come here to stop him robbing the country."
The demonstrators were planning to submit a petition to the Royal Palace calling on King Bhumibol Adulyadej to remove the prime minister.
Many protesters are concerned over the deal done by Mr Thaksin's family last week to sell their nearly 50% share in the Shin Corp telecoms conglomerate to Singapore's state-owned investment firm, the BBC's Kylie Morris in Bangkok says.
Regulators have now said that Mr Thaksin's son probably did break the law by failing to disclose information about changes in his shareholdings, but the Securities and Exchange Commission said it found no evidence of insider trading, our correspondent says.
In his Saturday address, Mr Thaksin was defiant, rejecting resignation demands.
"If I was to resign, that would mean that I betrayed more than 19 million voters who elected me," he said.
"Only one person can tell me to resign: his majesty the king. If the king just merely whispers to me, 'Thaksin, you resign', then I will resign right away."
Mr Thaksin still enjoys considerable support in rural Thailand and has survived such crises before, our correspondent says.