The People's Democratic Reform Committee, which has been campaigning for six months for the ouster of the government, launched its "all-out final battle" after Yingluck Shinawatra was ordered to step down as Premier on Wednesday by the Constitutional Court over the illegal transfer of her security chief.
Another court yesterday indicted her for negligence over a controversial rice subsidy scheme and will face impeachment that could see her banned from politics for five years.
Though the court dismissed nine members of Yingluck's government, protesters now want to chase the remaining members of her cabinet from power.
Thousands of protesters, mostly members of Bangkok's middle classes and activists from southern Thailand, fanned out across the city after protest leader Suthep Thaugsuban issued instructions to overthrow the government and root out any traces of former leader.
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Five people were injured outside the Centre for the Administration of Peace and Order when they tried to topple concrete barriers that were topped with barbed wire.
Suthep said the president of the Supreme Court and the senate speaker now represent the remaining pillars of power in Thailand. They should act to form an interim government within a few days.
The protesters say Yingluck's government is controlled by her brother Thaksin Shinawatra, who was ousted by the military as prime minister in a 2006 coup. They say Shinawatra family has corrupted Thailand's democracy and want an un-elected "people's council" to step in.
Government supporters, known as "red shirts", have also planned a mass rally tomorrow.