A large crowd of People's Democratic Reform Committee (PDRC) protesters marched through Yaowarat yesterday.
The 5.1km walkabout, which started at 10am at Wat Tuek intersection, was aimed at discouraging people from voting in today's election.
The marchers walked along Charoen Krung Road to Si Phraya and Silom roads and finished at Lumpini Park about 6pm.
PDRC leader Suthep Thaugsuban wore red and said this was to show the colour belonged to all Thais, not only pro-government groups.
He said the march may upset some people who wanted to cast their ballots, but he believed eligible voters who opted not to cast ballots today would outnumber those who did vote.
"The caretaker government is moving ahead with the election despite a lack of legitimacy," Mr Suthep said.
"The administration wants the election to be held to whitewash itself and protect the Thaksin regime.
"Our demonstration is aimed at rooting out this regime. We don't want the election to be held, as it will be a tool for the government to stay in power."
Mr Suthep said he believed today's poll would be nullified as the election procedures did not meet constitutional requirements.
The demonstrators would not return home empty-handed until national politics was reformed, he said.
Yesterday's protest march drew supporters from various anti-government rally sites in Bangkok.
Many people waited for Mr Suthep with cash donations at the ready to be handed out to him.
Mr Suthep and other leading members had lunch at a restaurant amid tight security by PDRC guards.