The protesters are united by their opposition to Mr Thaksin, and their belief that he is still controlling the current Pheu Thai government.
The demonstrations are being led by Suthep Thaugsuban, a former Thai deputy prime minister who resigned from the opposition Democrat Party to lead the rallies.
The protesters tend to be urban and middle-class voters. About 100,000 rallied in Bangkok on 24 November, when the campaign kicked off.
The protests were largely peaceful for the first week but turned deadly when violence broke out near a pro-government red-shirt rally on 30 November. At least nine people have been killed since then.
There was a pause in the protests to mark the 86th birthday of King Bhumibol Adulyadej, but protesters then returned to the streets.