As one whose government was overthrown by a military coup in may 2014 a big risk: ten years in prison if she is found guilty of negligence in the management of a grant program to rice farmers by his government.
May 2014 - Steps down from her post after Thailand's constitutional court finds her guilty of abuse of power in another case.
Al Jazeera's Scott Heidler, reporting from Bangkok, said hundreds of Yingluck's supporters gathered outside the Bangkok Supreme Court to await the verdict but were not allowed in the vicinity.
A judge read out a statement saying Yingluck's lawyers had informed the court she could not attend the hearing because she was ill.
Now, when the court returns to the case next month, it's possible that Yingluck will be convicted and sentenced in absentia - just as her brother was nine years ago. A planned string of aggressive prosecutions against Yingluck was clearly created to terminate her political career once and for all.
Requesting anonymity, the senior source in the Shinawatras' Pheu Thai party said she left Thailand on Wednesday, adding "it's impossible she left without the military green light".
"I have told security authorities to find out if she is really ill and where she is", Gen Prayut said.
After the court adjourned, there was confusion in the crowd of Yingluck supporters outside who had expected to see the political icon appear.
Prime Minister Prayuth Chan-ocha, who heads Thailand's military government, said all routes out of the country were being closely monitored.
"Up until this point we have no information showing that Yingluck has exited via any of Thailand's border check points", Immigration police chief Nanthathorn Prousoontorn said.
The rice subsidy plan Yingluck oversaw paid farmers about 50 percent more that they would have made on the world market. Shinawatra's lawyer said the politician was unwell.
Some of Ms Yingluck's supporters outside the court on Friday expressed understanding at her failure to show.
Throughout his trial, this heiress of a rich family in the north of the country has defended this program as a necessary aid to support rice farmers are poor, who receive historically little assistance from the government. "It is hard to track her".
But others have been calling for her to be exiled. Thailand's road toward peace and reconciliation is likely to be rocky, even if today, Yingluck is no longer around.
Earlier on Friday, the court postponed the verdict until September 27, saying the prosecution didn't believe that Yingluck was ill.
"But she might not have understood what was going to happen to her. that she would become the victim of a political game".
He said he would appeal, but was told it was too late in the day to apply for bail so will spend the weekend behind bars. Or the pursuit for Yingluck will thrust her and her supporters back onto the political centre-stage, deepening the fractures between north-east and central Thailand.
He declined to be named because he was not authorised to speak on behalf of Yingluck.