Thailand's Constitutional Court is to rule tomorrow in an abuse of power case against Prime Minister Yingluck Shinawatra.

A guilty verdict would likely force her from office and possibly bring her supporters on to the streets.

That could lead to confrontation with anti-government groups who have been protesting in the capital, Bangkok, for six months in an attempt to topple Ms Yingluck.

The anti-government group also disrupted a general election in February that Ms Yingluck had been expected to win.

The crisis broadly pits Bangkok's middle class and royalist establishment against the mainly poor, rural supporters of Ms Yingluck and her brother, ex-premier Thaksin Shinawatra.

He was ousted by the military in 2006 and now lives in exile to avoid a jail term handed down in 2008 for abuse of power.

Ms Yingluck defended herself in court today against a charge relating to her transfer of National Security Council chief Thawil Pliensri in 2011, which opponents say was designed to benefit her Puea Thai Party and a family member.

She said the decision to transfer the security chief was made by a committee of ministers.

"I did not interfere in the decision process ... which should be for the benefit of the land," Ms Yingluck told the court.

"I have never benefited from any transfer of civil servants."

Some legal experts say her entire government will have to go if she is forced to step down, but her party rejects that.

She has led a caretaker administration with limited powers since dissolving parliament in December ahead of the election.

"We believe cabinet must continue its caretaker duties until a new cabinet replaces it. There is no reason why the whole cabinet should go with her," Noppadon Pattama, a legal adviser to Mr Thaksin, told Reuters.

"That would be like carrying out a double execution."