Thailand's military-appointed legislature on Friday voted to impeach former prime minister Yingluck Shinawatra for her role in overseeing a government rice subsidy program that lost billions of dollars.

The vote, which means Yingluck will be banned from politics for five years, came just hours after the attorney general's office announced separate plans to indict her on criminal charges for negligence related to losses and alleged corruption in the rice program.

No date has been set for the formal indictment, but if convicted Yingluck could face 10 years in jail. She was forced by a court ruling last May to step down from her job for illegally transferring a civil servant, and just days later the army staged a successful coup.

Security at the Government House and parliament was stepped up with police squads and army troops amid fears that Red Shirt activists, known to have been loyal to the Shinawatra family, might gather en masse in protest of Friday's impeachment.

Friday's moves are the latest salvos against Yingluck's brother, ex-prime minister Thaksin Shinawatra, who was toppled from his job by a 2006 coup after being accused of corruption, abuse of power and insulting the monarchy.

Thaksin, in exile to avoid a two-year jail sentence on a 2008 corruption conviction, has sought a political comeback both through the pressure of sometimes violent street demonstrations by his so-called Red Shirt supporters, and more successfully through proxies at the ballot box.