BANGKOK (Reuters) - Thai authorities dealt a double blow to ousted Prime Minister Yingluck Shinawatra and her powerful family on Friday, banning her from politics for five years and proceeding with criminal charges for negligence that could put her in jail.
The moves could stoke tension in the politically divided country still living under martial law after the military seized power in May, toppling the remnants of Yingluck's government to end months of street protests.
The ban and the legal case are the latest twist in 10 years of turbulent politics that have pitted Yingluck and her brother Thaksin, himself a former prime minister, against the royalist-military establishment that sees the Shinawatras as a threat and reviles their populist policies.
Yingluck will face criminal charges in the Supreme Court and if found guilty could spend up to 10 years in jail, the Attorney General's Office said on Friday.
The charges against the country's first female premier, who was removed from office for abuse of power in May, days before the coup, concern her role in a scheme that paid farmers above market prices for rice and cost Thailand billions of dollars.
Yingluck vowed to fight the charges.
"Thai democracy has died along with the rule of law," she said in a statement posted on her Facebook page.
"I will fight until the end to prove my innocence, no matter what the outcome will be. And most importantly, I want to stand alongside the Thai people. Together we must bring Thailand prosperity, bring back democracy and truly build justice in Thai society."
There was no sign of protests on the capital's busy streets on Friday, as residents adhered to the junta's ban on public gatherings.
Security was tightened around the parliament building where the legislature, dominated by the military, voted Yingluck guilty in a separate impeachment case for failing to exercise sufficient oversight of the rice subsidy scheme.
The retroactive impeachment at the National Legislative Assembly (NLA) carries a five-year ban from politics.
A spokesman for the State Department said the United States had taken note of the retroactive impeachment by an appointed legislative body, and Assistant Secretary of State Daniel Russel would discuss U.S. concerns when he visits Bangkok on Monday.
"We believe that the impartial administration of justice and rule of law is essential for equitable governance and a just society," Jen Psaki told a regular news briefing. "It is a matter for the Thai people to determine the legitimacy of their political and judicial processes."
Washington, a long-time ally of Thailand, expressed dismay at the coup and responded by freezing $4.7 million of security-related aid, as well as cancelling high-level engagements and some military exercises and military and police training programs.
Russel will be the most senior U.S. official to visit Thailand since the coup.
Yingluck defended the rice scheme and disputed the charges in a NLA hearing on Thursday, but did not appear on Friday.
A vote to impeach required a three-fifths majority among NLA members, who were hand-picked by the junta of coup leader and Prime Minister Prayuth Chan-ocha. Around 100 of the 220 members are former or serving military officers.
Prayuth said he had not ordered the NLA to vote against Yingluck, still popular among the rural poor who handed her a landslide electoral victory in 2011 and benefited from the rice scheme.
The impeachment was expected by Yingluck supporters, who see the courts and NLA as biased and aligned with an establishment intent on blocking the Shinawatra family from politics.
"Yingluck's case was not dealt with fairly," said Thanawut Wichaidit, a spokesman for the pro-Yingluck United Front for Democracy against Dictatorship.
"The intention of these actions is for Yingluck and the entire Shinawatra family to be eradicated from Thai politics. I believe there is an invisible hand behind Yingluck's impeachment."
Around 150 members of the Shinawatra political movement have been banned from politics in the last decade, including four who had served as prime ministers.
Prayuth's government has urged Yingluck's supporters to stay out of Bangkok this week, although a repeat of the protests that have dogged the country in recent years appears unlikely.
Authorities have been quick to stifle dissent, and political meetings are banned under martial law.
In a radio broadcast, Army Chief General Udomdej Sitabutr called on the population to respect the NLA vote, and a spokesman for the junta said it had seen no sign of unrest.
"Political gatherings cannot happen as we are still under martial law," junta spokesman Winthai Suvaree said.
Yingluck's fortunes have been similar to those of her billionaire brother.
Both led populist governments toppled in coups, despite being elected in landslides, and both were subjected to legal action and street protests by pro-establishment activists.
After being ousted in 2006, Thaksin fled Thailand to avoid a 2008 jail term for corruption. He has lived abroad since, but retains a strong influence over Thai politics.
Yingluck did not plan to flee, said Singthong Buachum, a member of the former prime minister's team.
"She will fight the case head on," Singthong said.
Prayuth has promised a return to democracy after the junta enacts political and social reforms. His government has said a general election will take place in February next year at the earliest.
Additional reporting by Kaweewit Kaewjinda and Aukkarapon Niyomyat in Bangkok and David Brunnstrom in Washington; Writing by Amy Sawitta Lefevre and Simon Webb.; Editing by Jeremy Laurence, Nick Macfie and Andre Grenon