As the registration of migrant labourers reaches its deadline on Saturday, over 14,000 undocumented workers have still not completed the process, Labour Minister Adul Sangsingkeo said.
He urged employers to ensure all their staff were legally registered with the ministry's one-stop service (OSS) centres. An estimated 14,298 people, mostly from neighbouring countries, are now suspected to still be working in Thailand illegally.
Of them, 9,966 are from Cambodia, 1,728 from Laos and 2,604 from Myanmar.
The ministry started registering migrant labourers last year with the aim of documenting and regulating 1.32 million people, the vast majority from the aforementioned three countries. But the process has been plagued with problems and delays.
Only 840,736 labourers were registered in May, leading the deadline to be pushed back a month.
Since then over 333,000 people have scrambled to register at the OSS centres, half from Myanmar.
"We would like to thank those three countries for their full cooperation in verifying the nationality of these now-documented migrant workers," Pol Gen Adul said.
"I would also like to reiterate that from [today], any undocumented workers will not be allowed to stay and work in the country," he said.
"From [tomorrow], the ministry's employment department will be working closely with local police and relevant agencies to strictly enforce this law," he added.
According to the 2017 executive decree on the management of migrant workers, legal action will be pursued against both employers and unregistered staff in the event of any visa-related transgressions.
Labourers will face a fine of 5,000 to 50,000 baht. They will also be repatriated and banned from working in Thailand for two years.
Employers will face a fine of 10,000 to 100,000 baht per illegal worker.
Repeat offenders will be liable for fines of 50,000 to 200,000 baht per worker, a jail term of not more than one year, and a three-year ban on hiring foreigners.
Meanwhile, Suradet Walitthikun, secretary-general of Social Security Office, insisted yesterday the number of migrants using healthcare benefits under the Social Security Fund were comparable to the number of Thais taking advantage of these.
But proportionally more migrant workers are using the medical benefits compared to Thais in provinces like Bangkok, Samut Prakan and Samut Sakhon, where their birth rates are higher, he said.
Mr Suradet's remarks comes as over a million legally registered migrant labourers were found to be entitled to seven benefits under the fund -- similar to Thai employees. Those from Myanmar stood to benefit the most.
They cover illness, disability, death, child delivery, pensions and more.