Bangkok: Thousands of police and soldiers are set to be deployed across the Thai capital ahead of a verdict on Friday in the trial of former prime minister Yingluck Shinawatra​ likely to inflame tensions in the military-run country.

For days security forces have manned check-points outside Bangkok where they've been turning away supporters from of Ms Yingluck's rural heartland who wanted to mass outside the court.

But thousands are still expected to defy a ban on public gatherings of more than five people and turn up to learn the fate of  Thailand's first female prime minister who has been accused of negligence in her handling of a failed rice subsidy scheme that cost Thailand $US8 billion $10 billion) in losses.

Police said they are "100 per cent prepared" to confront troublemakers.

Prime Minister Prayuth Chan-ocha, an army general who led a coup to topple Ms Yingluck's government in 2014, warned supporters against mass protests, saying "why even go? Let the courts do their job."

Ms Yingluck's lawyer Norawit Lalaeng told reporters she would show up despite predictions she would flee the country like elder brother, Thaksin Shinawatra​, a divisive figure who faced two years' jail on corruption charges he insists were politically motivated.

"The former prime minister feels encouraged as she has received a lot of moral support from the people," Mr Norawit said.

Earlier Ms Yingluck said "it is the pride of my life that I had a chance to implement this policy for rice farmers".

Ms Yingluck has pleaded not guilty in the case that her Red Shirt movement sees as a witch-hunt by the government.

Critics say the military establishment wants to rid Thailand of the Shinawatra political machine that has been clobbered by courts and coups despite winning the country's last five general elections. Family loyalists have been sacked or transferred from government jobs.

The government has already frozen Ms Yingluck's bank accounts and imposed a $US1-billion fine over the rice subsidy scheme. 

Analysts say the case is likely to have far-reaching implications for the country where deep political divisions remain after a decade of sometimes violent upheaval.

Ms Yingluck has not been accused of corruption but prosecutors argued in court that she ignored warnings of corruption in the subsidy program. She could face up to 10 years in jail if convicted.

A conviction would set a precedent for Thai leaders to be charged over failed government policies.

If the court sentences Ms Yingluck to jail she would have 30 days to appeal.

But a jail sentence would draw huge sympathy from her support bases in the country's north and north-east and could stoke the first unrest since the 2014 coup.

If the court dismisses the charge the government is likely to appeal against the dismissal.

Ms Yingluck promised the subsidy scheme during her 2011 election campaign which observers at the time saw as her way of mimicking Mr Thaksin, who introduced popular expansionist economic policies in rural areas before he was ousted.

The plan was to buy up local rice harvests for as much as 50 per cent above market rates to drive up global prices. But the market saw it as a clumsy attempt at price manipulation.

Rice exporters such as Vietnam and India stepped up production while Thai exporters responded by investing in emerging producers such as Cambodia, Laos and Myanmar.

The government amassed huge stockpiles of rice rather than sell at a loss overseas. Much of it rotted.