The protest leaders had promised 100,000 people would join their movement to oust the government.
In the end, only a fraction of that number showed up, according to the BBC's correspondent in Bangkok, Jonathan Head.
But their lack of mass support belies the serious threat they still pose to the four-month-old government of Prime Minister Samak Sundaravej, our correspondent adds.
His People Power Party - made up of Mr Thaksin's allies - won the elections in December 2007 that returned Thailand to democracy.
But the deep divisions that contributed to the military coup remain.
Mr Thaksin, a telecommunications billionaire, is banned from politics, but he still enjoys strong support in rural areas.
He is, however, deeply disliked by Bangkok's traditional elite, who do not want him to make a political comeback.
His opponents are also angry at the new government's recent move to amend the military-backed constitution - a move they say will give obvious benefits to the People Power Party and give Mr Thaksin added protection.
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