She is accused of negligence over a rice subsidy policy that funneled cash to her poor, rural farming base but cost the Thai exchequer billions of dollars.
Her supporters say the case is driven by the junta that booted her from office in 2014 and is determined to expunge her super-rich clan from Thailand's political scene.
Her brother Thaksin, who heads the Shinawatra family, was toppled as premier in a 2006 coup and fled the country over corruption convictions.
She wiped away tears as she embraced supporters and posed for pictures with the crowd of some 500 supporters massed outside of the Bangkok court, holding roses and balloons.
More From This Section
"I want to thank all of the media and people who came here to support me," she said in a brief comment to the press.
If the remaining witnesses are heard, Friday could see Yingluck give a final defence statement -- although legal argument could prolong the case.
Thailand's first female prime minister was impeached for abuse of power and banned from politics in the wake of the coup.
But she remains a galvanising force for the pro-democracy movement, with a common touch absent in most Thai politicians.
"People love the Shinawatra family because they helped small people get money and make a living," said Wachiraporn Laongnual, who said she travels two hours to attend every court hearing.
The former PM was joined by dozens of Pheu Thai politicians on the steps of the court, a rare gathering for a political camp that is barred from meeting under junta controls.
The Shinawatras and their allies have won every general election since 2001, but their political networks have been battered by the coups and endless legal cases.
The Thai junta, which represents the royalist Bangkok- centric elite, refuses to accept the legitimacy of Shinawatra electoral victories, decrying their politics as venal and corrupt.
Yingluck also faces a civil action to claw back $1 billion in compensation for the rice subsidy program that paid farmers up to twice the price of their crop.