Thailand's Constitutional Court says it will deliver a verdict Wednesday on the abuse of power charges against Prime Minister Yingluck Shinawatra.
The prime minister, who could be removed from office if found guilty, defended herself before the Bangkok court Tuesday.
"With all my respect to the judges, I would like to take this opportunity to deny the allegations I am accused of."
The charges relate to the 2011 replacement of Ms. Yingluck's then national security chief. Her critics say the move was unconstitutional and meant to benefit her Pheu Thai Party.
Separately, Thailand's Anti-Corruption Commission has charged Ms. Yingluck with dereliction of duty over a government rice-buying scheme that critics say is wasteful and corrupt.
The prime minister has survived months of protests aimed at toppling her government, but the court cases now present a new challenge to her rule.
Ms. Yingluck's supporters say the cases are politically motivated. They have threatened to stage mass protests if she is removed from office, raising fresh concerns about violence.
Around two dozen anti-government protesters have been killed during clashes with police and attacks on demonstrations in the past several months.
The opposition protesters say Ms. Yingluck's government is hopelessly corrupt and controlled by her brother, ex-prime minister Thaksin Shinawatra.
Mr. Thaksin was removed from office in a 2006 military coup. The billionaire businessman is still very influential in Thailand. He is living in exile to escape corruption charges.
Ms. Yingluck already called for early elections in February, but the opposition boycotted the vote and disrupted it in many provinces with protests.
Last week, the prime minister and the election commission agreed to hold another election on July 20, but it is unclear if the opposition will participate this time.