Protesters are blocking roads in parts of the Thai capital, Bangkok, in a bid to oust the government before snap elections on 2 February.
The protesters have built barricades and occupied key road junctions.
The government has deployed 18,000 security personnel to maintain order.
The protesters, who began their campaign in November, want to replace the government of Prime Minister Yingluck Shinawatra with an unelected “People’s Council”.
They allege Ms Yingluck is a proxy for her brother, former Prime Minister Thaksin Shinawatra, who was ousted by the military in 2006 and is currently in self-imposed exile.
Protesters claim populist policies from Thaksin-allied parties have created a flawed democracy.
However, Thaksin-allied parties draw considerable support from rural voters and have a majority in the Thai parliament. Parties allied to Mr Thaksin have won the last four elections.
