Thai Prime Minister Yingluck Shinawatra arrived at the Constitutional Court on Tuesday to defend herself against charges of abuse of power, one of two legal challenges that could see her removed from office this month.
Six months of street protests aimed at toppling Yingluck have undermined her government, but she has clung on and the number of protesters has dwindled.
However, tension is rising again, with her supporters threatening action if the courts remove her and fears of confrontation with the protesters growing.
Both her supporters and the anti-government protesters plan large rallies in or around Bangkok next week.
Yingluck is charged with abuse of power over her transfer of National Security Council chief Thawil Pliensri in 2011, which opponents say was designed to benefit her Puea Thai Party. If found guilty, Yingluck could be forced to step down and some legal experts say her entire government would have to go too.