BANGKOK (AFP) - Thailand's ex-premier Yingluck Shinawatra arrived for the hearing of impeachment proceedings, initiated against her by the army-stacked National Legislative Assembly (NLA), for driving through a costly rice subsidy scheme.

Thailand's first female premier was removed from office by a court ruling shortly before the military coup in May knocked out the rump of her administration.

Observers say a vote to impeach her - which carries an automatic five-year ban from politics - could stir her "red shirt" supporters to protest, ending months of relative calm since the army grabbed power and imposed martial law on the kingdom.

But junta chief Prayut Chan-O-Cha, the current prime minister, has shrugged off any potential revival of the street protests which have blistered Thailand's recent political history.

"There will be no protest, they can't protest. If they don't accept the ruling, we will take action, that's it," he told reporters earlier.

"What is the condition of martial law? No political movement," he said, urging the public to allow the NLA to reach its conclusion, which is due before the end of the month.

A successful impeachment needs three fifths of the 250-strong national legislature to vote in favour.

Critics say the NLA is driving through a junta-led agenda to dismantle the power base of Thaksin Shinawatra - Yingluck's older brother who lives in self-exile to avoid jail for a corruption conviction.

"Driving her (Yingluck) out of politics could instigate resentment among her political supporters," said Thai academic Pavin Chachavalpongpun, of Kyoto University.

Thaksin, who was deposed as premier in a 2006 coup, sits at the heart of Thailand's deep schism.

He is loathed by the Bangkok-centred establishment and its supporters among the judiciary and army, but still enjoys support in the nation's poor but populous northern half.

Shinawatra-led or aligned parties have won every election since 2001.