About 50,000 people gathered in Bangkok on Sunday, to take part in a protest against Thai Prime Minister Thaksin Shinawatra.
Buddhist monks and nuns featured prominently in the demonstration - the latest in a series aimed at forcing the prime minister to stand down.
The authorities had feared violence might erupt, but the demonstration was peaceful - and at times festive.
Sondhi Limthongkul, a media tycoon and leading critic of the prime minister, said the protests would continue until Mr Thaksin stood down.
The demonstrators accuse Mr Thaksin of corruption and abuse of power - but the prime minister insists he will stay on until a snap election in April.
The activists rallied near Democracy Monument, the focal point of violent protests that brought down the Thai military government in the 1990s.
Thousands eventually took part in an unscheduled march towards the prime minister's office.
The protesters negotiated their way past riot police armed with batons, who briefly tried to stop them.
The protestors held a sit-in outside Government House, and listened to speeches by their leaders, as police looked on.
The protest went on into the night, before activists returned to Sanam Luang, a public square where many are camping.