
The US "expressed our grave disappointment to Thailand," State Department spokesman John Kirby said.
"We condemn Thailand's forced deportation on July 9 of over 100 ethnic Uighurs to China, where they could face harsh treatment and a lack of due process," the department said in a statement.
The fate of a group of Uighurs in Thailand had been in doubt after Thailand sentenced them for illegal entry to the country in 2014.
Thailand announced the deportation Thursday of the Uighurs, a Muslim minority in China's northwest who speak Turkic and have often opposed Chinese control.
It was also revealed that some of the group had been sent to Turkey in June.
Anti-Chinese protesters stormed the Thai consulate in Istanbul in protest of the controversial deportation, the latest demonstration in the country over China's treatment of Uighurs.
Human rights groups say Uighurs who flee China face possible torture and other abuses if returned.
There are around 10 million Uighurs in China's northwest Xinjiang region and many say they face cultural and religious repression.
"This action runs counter to Thailand's international obligations as well as its long-standing practice of providing safe haven to vulnerable persons," the State Department said in the statement, urging the country to halt further deportations.
Aid organizations should have "unfettered" access to the Uighurs and Thailand should respect its international obligations not to expel refugees, the US said.
"We urge Thailand to allow those remaining ethnic Uighurs to depart voluntarily to a country of their choice."