Thai authorities have banned former Prime Minister Yingluck Shinawatra from office for five years and launched a legal case that could see her jailed.
An army-appointed legislature impeached her over corruption in a scheme she oversaw to subsidise rice farmers.
The criminal charges, which also relate to the rice scheme, could result in a 10-year jail term.
The military has ruled Thailand since May 2014, when they overthrew Ms Yingluck’s government in a coup.
The BBC’s Jonathan Head in Bangkok says the impeachment sends a strong signal that there will be no compromise and her family will be removed from politics.
Ms Yingluck and her brother, tycoon and former Prime Minister Thaksin Shinawatra, remain hugely popular among Thailand’s rural poor, but are hated by an urban and middle-class elite who accuse them of corruption and abuse of power.
Their party is the most popular in Thailand and has – under various different names – won every election since 2001.
Shortly after her impeachment, Ms Yingluck was due to hold a news conference at a Bangkok hotel.
But troops arrived and prevented her from speaking.
Thailand is still under martial law and unauthorised political meetings are banned.
Ms Yingluck has since posted a statement (in Thai) on her Facebook page accusing the authorities of trying to destroy her.
“Democracy has died in Thailand today, along with the rule of law,” she said.