They insist they are fighting for democracy, seeking to end political meddling by the appointed elite.
And, from the start, the mainly rural poor and urban working-class Red Shirts have been demanding that unelected Prime Minister Abhisit Vejjajiva must go.
Heading a coalition cobbled together with help from the military, he holds the post their populist hero Thaksin Shinawatra was ousted from in 2006.
Thaksin has kept in touch with his supporters by video-link from self imposed exile. He fled Thailand two years ago, accused of undermining its powerful monarchy and breaching conflict of interest laws. He was sentenced in absentia to prison.
One unifying figure is the country’s king whose political influence is accepted by most Thais. But King Bhumibol Adulyadej, 82, is in ill health and has been in hospital since last September.