Ms Yingluck, the kingdom's first female premier and the sister of former leader Mr Thaksin Shinawatra, was toppled from office by a controversial court ruling shortly before the army staged a coup in May.
She faces impeachment by the military-appointed National Legislative Assembly over her administration's loss-making rice programme, which funnelled cash to her rural base, but cost billions of dollars and was a driving force behind protests that felled her government.
A successful impeachment needs three-fifths of the 250-strong assembly to vote in favour when they meet next Friday.
A guilty verdict would bring an automatic five-year ban from politics, but also risks enraging her family's 'Red Shirt' supporters who have laid low since the coup.
"Although she is no longer in her position she still has to face a political punishment," said commissioner Vicha Mahakhun of the National Anti-Corruption Commission.
Ms Yingluck did not appear at her second hearing on Friday -- sparking indignation among anti-Shinawatra assembly members who refused to hear from former ministers sent to represent her.
Experts say the impeachment move is the latest attempt by Thailand's royalist elite, and its army backers, to nullify the political influence of the Shinawatras, whose parties have won every election since 2001.
The NACC led the probe into the rice scheme which paid farmers up to twice the market rate for their grain but left Thailand with a mountain of unsold rice.
"We warned the government twice (over the rice scheme) but the government ignored us," Vicha said, adding he hoped the Attorney-General would "agree" to also pursue a criminal charge against her over the scheme.
Mr Thaksin, who was deposed as premier in a 2006 coup, is reviled by the Bangkok-based establishment, its supporters in the south and among the judiciary and army, but still pulls on the loyalty of the north and among sections of the urban middle and working classes.
A vote to impeach Ms Yingluck could stir the Red Shirts to protest.
But junta leader General Prayut Chan-O-Cha, who is also the prime minister, played down the prospects of fresh protests and violence ending months of relative calm since the army grabbed power and imposed martial law.
"I can't let that happen. I will enforce the law," Gen Prayut added.
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