The case hands the ruling junta its first big test of 2015 given Yingluck's popularity among millions of rural poor who elected her in a 2011 landslide.

Yingluck was removed from office in May after a court found her guilty of abuse of power, days before the military staged a coup after sometimes violent protests against her government that began in November 2013.

A day after she was removed, the country's anti-corruption body indicted her for dereliction of duty in relation to a controversial rice subsidy scheme.

The National Anti-Corruption Commission found her guilty of mishandling the rice scheme, estimated to have cost $15 billion in losses. The National Legislative Assembly (NLA) due to rule on Yingluck's impeachment was hand-picked by those behind last year's coup.

The hearings start on Friday and a decision could come by the end of this month, the NLA said. If impeached, Yingluck faces a five-year ban from office.

The junta has overseen a period of political stability but has struggled to revive the economy, Southeast Asia's second-biggest, which grew just 0.2 percent in the first nine months of 2014 due to weak exports and subdued domestic demand.

Critics say the case is part of the junta's ambition to end the influence of Yingluck's powerful family and any move to impeach her could raise the specter of a backlash by her supporters.

"If Yingluck is removed it could ignite resistance to the military government," said Thanawut Wichaidit, a spokesman for the pro-Yingluck United Front For Democracy against Dictatorship group.

Martial law is still in place nationwide and protests are banned, but that has not stopped some farmers and activists from staging small rallies against the junta.

Years of crisis have centered largely around Yingluck's billionaire brother Thaksin, whose populist policies won him huge support but upset the military-backed establishment.

Thailand plunged into political crisis after Thaksin, whose parties have won every election since 2001, was deposed in a 2006 coup.