Thailand's caretaker Cabinet has appointed an acting prime minister, after the Constitutional Court ordered Prime Minister Yingluck Shinawatra and several Cabinet members to step down.
The Cabinet appointed Commerce Minister Niwatthamrong Boonsongphaisan to take over.
The Bangkok court unanimously ruled Wednesday that Prime Minister Yingluck improperly transferred her national security chief to another job in 2011. It said the move was unconstitutional and done for her own benefit.
Prime ministers are usually chosen by the country's lower house of parliament. But Ms. Yingluck dissolved that body last year when she called for early elections to try to resolve the country's political crisis.
Ms. Yingluck insists she did nothing wrong. Her supporters say the charges are politically motivated. They plan to protest her forced resignation.
U.S. State Department spokeswoman Jen Psaki is urging all sides to resolve their political differences peacefully, saying violence is unacceptable.
She said any resolution on Thailand should include an election for a new government.
Anti-government street protests in Thailand have killed about 25 people since the start of the year.
After failing to force Ms. Yingluck to resign, the opposition turned to the courts. Opposition leaders 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 lives in exile to escape corruption charges.
Thailand's political turmoil pits Bangkok's urban middle class and royalist elite against the mostly poor, rural supporters of Ms. Yingluck and Mr. Thaksin.