"People died here," chanted more than 1,000 members of the United Front for Democracy against Dictatorship (UDD), better known as the Red Shirts.
The demonstrators were also there to show support for the current government, even though last week it pushed through an amnesty bill that would pardon leaders of the previous government who ordered the the dispersal of their protest camp in the middle of the city.
"We disagree with the amnesty but we don't want to see this government fall because of growing pressure frome the opposition," said Thawon Songprasom, 50.
In April-May, the UDD led tens-of-thousands in Bangkok to pressure former prime minister Abhisit Vejjajiva to dissolve parliament.