Thailand on Saturday sentenced dozens of asylum seekers thought to be from China's Uighur minority for illegal entry, an official said, despite a US appeal for their protection.

About 120 adults among the group were fined 4,000 baht ($124) each by a court in southern Thailand, according to police, who said they were waiting to identify the families before deciding their fate.

The men will be detained by immigration and the women and children will be taken to a shelter, Police Major General Thatchai Pitaneelaboot said by telephone.

The group of roughly 200 people was discovered in a raid on a suspected people smuggling camp on Wednesday in the kingdom's deep south.

They presented themselves to police as Turkish, but US-based activists have identified them as Uighurs, a Turkic-speaking, predominantly Muslim group from China's northwestern Xinjiang region.

Thailand, which says their nationality is still unconfirmed, has not said whether they might be forced to return to China, but the kingdom has a history of repatriating illegal immigrants.

The Turkish embassy and the UN refugee agency have been providing assistance.

On Friday the US State Department urged Thailand "to provide full protection" to the asylum seekers.

The latest annual US human rights report said that China carries out "severe official repression" of Uighurs in Xinjiang, including over their freedom of speech and religion.

Xinjiang is periodically hit by violent clashes and Chinese officials blamed Uighur separatists for a March 1 mass stabbing at a train station in the southwestern city of Kunming that killed 29 people and injured 143 others.

Under pressure from Beijing, countries including Cambodia, Malaysia and Pakistan have all in recent years forcibly returned Uighurs to China.

The Uighur American Association, a Washington-based advocacy group, voiced concern over the group, which it described as Uighurs, and urged Thailand to cooperate with the UN High Commissioner for Refugees.

"This group of Uighurs should not be a test of Thailand's relationship with China, but a test of Thailand's ability to follow international refugee standards," said association president Alim Seytoff.

Thailand has long been a hub for people trafficking, with thousands of Rohingya boat people from neighbouring Myanmar believed to have passed through the kingdom in recent years.