BANGKOK (AFP) - Thailand's ousted prime minister Yingluck Shinawatra appeared in court Tuesday for the start of a trial that could see her jailed for a decade, part of what observers say is a vendetta against her family.

Around 50 supporters gathered outside Thailand's Supreme Court on the northern outskirts of Bangkok, including more than a dozen members of Yingluck's Pheu Thai Party, a highly unusual sight in a country where political gatherings of more than five people remain banned by the junta.

Many burst into applause and shouts of "Yingluck, fight, fight!" when her convoy pulled up outside the courthouse for the trial, which is expected to last months. "I am confident that I am innocent and I hope the court will give me justice and allow everything to proceed in accordance with the law," Yingluck told reporters.

The ousted premier is accused of criminal negligence over a populist rice subsidy scheme, which paid farmers in the rural Shinawatra heartland twice the market rate for their crop.

She is not accused of personal corruption but of failing to prevent alleged graft within the programme, which cost Thailand billions of dollars and galvanised protests against her elected government prior to last May's coup. The charge carries up to 10 years in jail.

It is the latest legal move against Yingluck - sister of fugitive billionaire former premier Thaksin Shinawatra - whose administration was toppled in a military coup nearly a year ago.

A guilty conviction could deliver a hammer blow to the political dominance of her family, but it also risks stirring up their grassroots "red shirt" supporters who have remained largely inactive since the military took over.

Thailand's military-appointed Parliament impeached Yingluck in January over the scheme, a move which banned her from politics for five years.

"I believe a hawkish faction in the old powers... wants to punish the Shinawatras as much as they can," Ms Puangthong Pawakapan, a Thai politics expert at Chulalongkorn University, told AFP.

"But keeping her in prison will definitely anger the red shirts even more," she added.

Other analysts say the mere threat of jail may be used to discourage the Shinawatras from re-engaging in politics.

Yingluck herself has said the rice scheme "lifted the quality of life for rice farmers" in the poor north-east of a country where subsidies to farmers have long been a cornerstone of Thai politics.

The army takeover last year was the latest twist in a decade of political turbulence that broadly pits a Bangkok-based elite, backed by parts of the military and judiciary, against poor urban and rural voters, particularly in the country's north, who are fiercely loyal to the Shinawatras.

Thaksin was himself toppled by a previous coup in 2006 and now lives in self-exile to avoid jail on a corruption charge.

The Shinawatras, or parties allied to them, have won every Thai election since 2001.

But their opponents accuse them of cronyism, corruption and financially ruinous populist policies.

As a result, the Shinawatra family have faced two coups and the removal of three of their premiers by the Thai courts, while several deadly rounds of protest have rocked Bangkok and weighed on the Thai economy.

Former prime minister Somchai Wongsawat, brother-in-law to Yingluck and Thaksin, is also facing criminal charges over a crackdown against anti-Shinawatra protesters in 2008.