Thai Prime Minister Yingluck Shinawatra has dissolved parliament and called an election after sustained protests in the capital, Bangkok.
All opposition MPs resigned from parliament on Sunday, and protesters marched again on Government House.
Ms Yingluck won a huge majority in the last election in 2011.
But the protesters say her government is controlled by her brother, ousted leader Thaksin Shinawatra, and have vowed to continue demonstrating.