Thailand last month sent at least 40 Uyghurs back after they had spent years in Thai detention facilities after fleeing China more than a decade ago.

The move sparked international condemnation, with the United States announcing visa bans last week for Thai officials involved in the deportations.

Thailand defended its decision, saying it had "received assurances" from China that the Uyghurs would be treated well.

On Wednesday Deputy Prime Minister Phumtham Wechayachai -- who also serves as defence minister -- and Justice Minister Tawee Sodsong arrived in Kashgar for an official visit.

The ministers were met by Qi Yanjun, a Chinese vice minister for public security, who briefed them on the Uyghurs' treatment since their return, the Thai defence ministry said in a statement to journalists.

Qi told them that most of the Uyghurs had returned to their homes, but some were being treated in hospital, the statement said.

The Thai delegation is to visit some of the Uyghurs at their homes -- on visits arranged by the Chinese authorities.

"We will see what they allow us to access, given the time constraints," Phumtham told reporters late Tuesday evening at a military airport in Bangkok before his departure.

He added that he is scheduled to meet with doctors to inquire about the deportees' conditions.

"We will try our best, but their homes are quite far apart, and Xinjiang is three times larger than Thailand," he said, adding that those who cannot be visited in person will be contacted by video call.

Rights groups and Uyghurs overseas allege that China has detained more than a million Muslims, mostly Uyghurs, in a network of facilities in Xinjiang that are rife with violence, torture, forced labour, political indoctrination and other abuses.

Beijing vehemently denies the accusations, saying its policies in Xinjiang have eradicated extremism and boosted development, and that the facilities were voluntarily attended training centres that closed years ago after attendees "graduated".

China's Foreign Ministry Spokeswoman Mao Ning, asked about the Thai visit, said the repatriations were entirely legal.

"This was normal law enforcement cooperation between China and Thailand in accordance with the laws of both countries, international law and international convention," she said at a regular briefing.

"The relevant personnel have had their legal rights fully guaranteed."

Human Rights Watch has urged the Thai officials to use their trip to demand "unfettered" access and to publicly press China about "their abuses against Uyghurs".

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