Most protesters left by morning, but some vowed to stay on
Thai Prime Minister Thaksin Shinawatra has dismissed calls for him to step down, after thousands of demonstrators held another anti-government rally.
"I will not resign, because [it] will not resolve anything," Mr Thaksin said.
At least 50,000 protesters marched to Bangkok's Government House on Sunday, chanting "Thaksin out!"
This is the latest in a series of rallies accusing Mr Thaksin of abuse of power. He has called a snap election in April to try to regain authority.
But the main opposition Democrat Party and two other parties have said they will boycott the poll.
Analysts say that the absence of a serious alternative to Mr Thaksin's Thai Rak Thai party seriously threatens the election's legitimacy.
On Sunday afternoon, anti-Thaksin demonstrators gathered in Sanam Luang, near Bangkok's Royal Palace, the venue where Mr Thaksin drew some 150,000 supporters on Friday for his own rally.
As Sunday evening wore on, different speakers came on stage to castigate the prime minister, burning an effigy of him in a mock funeral.
Then the organisers called on the crowd to march towards Government House.
There were a few tense moments as protest leaders negotiated their way past police lines, but the rally remained largely peaceful as the large flag-waving procession snaked through the streets.
The majority of the protesters have now dispersed, but about 2,000 people have vowed to camp at Sanam Luang until Mr Thaksin resigns.
Most are members of the Buddhist Santi Asoke sect, whose leader is Chamlong Srimuang, a former general who led a successful uprising against the military-led government in 1992.
Other anti-Thaksin activists, who include many people from Bangkok's middle classes, have been encouraged to reassemble every day, after working hours.
Mr Thaksin, who has said he will resign if his party does not win at least 50% of the vote in the election on 2 April, has already started his election campaign.
He is currently in the north-east, shoring up the high level of support he still enjoys in rural Thailand.
Critics of Mr Thaksin say he has destroyed democratic institutions and is guilty of corruption, tax evasion and human rights violations.
He has also been criticised for his handling of an insurgency in the south of the country. Violence in the area continued on Monday, with three people killed when a group of about 10 attackers opened fire on two Buddhist households in Pattani province, police said.