Yingluck, Thailand's first female premier and the sister of fellow ousted premier Thaksin Shinawatra, was removed from office in a controversial court ruling shortly before the army toppled the remnants of her elected government on May 22.
Despite being forced out of office, the military plan to impeach her over her administration's loss-making rice subsidy programme which -- while popular among her rural powerbase -- was a driving force behind protests against her now toppled government.
"The opening of impeachment set on January 9 at 10am and I think the whole process will take about 30 days," assembly member Jetn Siratharanont told AFP.
Yingluck's legal team had hoped to delay the hearing so they could gather more evidence but their request was denied.
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Analysts say the impeachment proceedings are part of a wider campaign to make sure her family -- who are loathed by the military and Bangkok-based royalist establishment -- cannot enter office again.
"The junta is trying to install infrastructure, through drafting a new constitution and also through a series of pending cases, to make sure that if there is ever another election someone like Yingluck -- or someone closely associated with her -- will not be able to stand," he added.