Images posted on social media purport to be of protesters heading for the Thai PM's empty house, where riot police are said to be deployed.
It comes after Thai security forces have fired tear gas at anti-government protesters who stormed a stadium in the capital to try to prevent political parties registering for upcoming elections.
Prime Minister Yingluck Shinawatra has faced weeks of mass street rallies seeking to curb her family's political dominance and install an unelected "people's council" to oversee electoral reforms.
The protests have left five people dead and more than 200 wounded in street violence, although tensions had abated since several days of clashes between police and demonstrators in early December.
Yingluck has called a snap election for February 2 to try to ease tensions, but the main opposition Democrat Party - which has not won an elected majority in about two decades - has vowed to boycott the vote.
The latest confrontation came as representatives of about 30 political parties gathered inside a Bangkok stadium for a draw for the numbers to be used on the ballot sheets.
The demonstrators have vowed to keep up their campaign to disrupt the polls, with protest leader Suthep Thaugsuban threatening to "shut down the country" to prevent people voting.
Pictures on social media show protesters injured during the clashes.
