More than 300,000 immigrant workers will be deported after the nationality verification (NV) deadline ended on Friday last week.
Pravit Khiengpol, chief of the Department of Employment, said migrant workers who failed to apply for NV by the deadline are now required to report to immigration offices at border provinces to be deported.
Of those facing deportation, 150,000 are Cambodians, 99,000 are Lao and 60,000 are Myanmar, he said.
Mr Pravit said those who turn up for voluntary deportation will not face legal action.
Employers seeking to legally recruit migrant workers can now submit their requests with provincial labour offices, he said.
From now on, migrant employees will work under a memorandum of understanding designed to enable workers from neighbouring countries to enter Thailand through legal channels to meet specific skills shortages and employer demands.
Mr Pravit also advised employers who want to keep unverified migrants to submit requests with provincial labour offices so the authorities can ask their embassies to issue passports for the workers.