Ousted Thai premier Yingluck Shinawatra will appear in court Friday for the start of a lengthy corruption trial that critics say is an attempt by the kingdom's generals to hamstring the popular leader and extend their political dominance.

Yingluck faces up to a decade in jail if convicted on charges linked to her administration's popular but financially costly rice subsidy scheme.

Thailand's first female prime minister was overthrown days before army chief Prayut Chan-O-Cha seized power in May 2014 amid street protests between rival political factions that have dogged the country for the last decade.

Under junta rule she has faced a string of legal challenges that her supporters say are politically-motivated, including a vote by the military-appointed legislature to ban her from politics for five years.

That ban and the current trial centred around accusations she failed to stop graft within her administration's rice subsidy program.

It cost the country billions of dollars and was seen by Yingluck's detractors as a populist handout to please her support base in the rural north and north-east.

But Yingluck has defended the policy as an effort to lift rice farmers out of poverty after decades of neglect by Bangkok's wealthy elite.

Analysts say her corruption trial is being used to legitimise the coup and bolster the generals' self-styled reputation as graft-busters.

"The junta continues to seek legitimacy and Yingluck's case provides a pretext for it to do so," Pavin Chachavalpongpun, a prominent Thai academic and critic of the military government who fled overseas after the coup, told AFP.

- Double standards -

Prayut has vowed to end Thailand's long history of expensive rural subsidies.

But his administration has been accused of employing double standards after the government this week agreed to buy thousands of tonnes of rubber at above market prices following protest and disruption threats from farmers.

Unlike rice farmers, who overwhelmingly support the Shinawatra clan, Thailand's predominantly southern rubber farmers played a key role in the street protests against Yingluck that led to the coup.

Yingluck's trial is scheduled to last until late 2016, with the first prosecution witness taking the stand today and the final defence testimony slated for November.

The former premier, who cannot leave the country without the government's permission, has been ordered to attend each hearing.

Thailand's decade of political conflict broadly pits a Bangkok-based middle class and royalist elite, backed by parts of the military and judiciary, against rural and working-class voters loyal to Yingluck and her brother Thaksin, who was also deposed in a coup in 2006.

Parties controlled by or linked to the Shinawatra clan have won every election since 2001.

But the movement's electoral dominance has been challenged by two military coups supported by the country's elite, and a slew of judicial rulings that have dissolved political parties and removed elected leaders.

The military's eagerness to quash the siblings' enduring popularity was on display earlier this month when authorities rushed to ban a calendar featuring Yingluck and Thaksin in an embrace.

Prayut had vowed to swiftly return power and hold elections once the country had been rid of corrupt politicians and stability restored. However the election dates keep slipping and he has employed increasingly draconian tactics to keep dissent in check.

The military has also struggled to kickstart the kingdom's lacklustre economy while recent corruption allegations over an army-built public park have tarnished their anti-graft image.