The Ministry of Labour on Monday pledged to document what it says are the remaining 10,000 illegal Cambodian migrant workers in Thailand by the end of June.
All remaining undocumented Cambodian workers after the deadline passes face repatriation by Thai authorities.
Labour rights groups, however, have said that the number of undocumented Cambodians working in Thailand is actually much higher and that they can face difficulties in completing the documentation process.
According to an announcement by the ministry, issued on Monday, the deadline for worker documentation will expire on June 30.
It said as of Monday, Cambodian officials and their Thai counterparts had documented 1,070,000 Cambodian migrant workers.
"Thailand has permitted undocumented migrants to return to Cambodia to get documented and return to work in Thailand", the announcement read.
It said Thailand will cooperate in good faith with Cambodia regarding the remaining undocumented workers and notify the Cambodian Embassy.
The ministry hailed the documentation drive as a "success" that benefits people of both countries.
However, Dy The Hoya, of labour rights group Central, said he believed the number of undocumented Cambodian migrant workers in Thailand was higher than the official figure.
He said the ministry may not be able to legalise all Cambodian undocumented workers in time, even after having extended the deadline on a number of previous occasions.
"The legal process has not been able to reach everyone. As for the ministry's figure of 10,000 illegal Cambodian workers, I would say the number of remaining undocumented workers is not below 20,000 or 30,000," he said.
Hoya said undocumented migrants faced difficulties in achieving full legal status.
"Migrant workers have told us that the legalisation process costs around 3,000-4,000 baht [around $90-$120], but some can spend up to 10,000 baht because unscrupulous employment brokers convince them that this is how much it costs," he said.
Hoya said another stumbling block to registration is a lack of understanding of the law among employers, especially the owners of smaller businesses.
"[But] for large registered companies, they know the process and have their workers complete it," he said.
Hoya said under the latest Thai law, illegal workers can be repatriated and their employers fined after the deadline expires.
However, he doesn't think punishments will be implemented too heavily as Thailand still needs migrant workers to fill employment shortfalls, he said.
Labour Ministry spokesman Heng Sour declined to comment, referring The Post to the ministry's announcement.