The Labour Ministry has launched a crackdown on migrant workers and their Thai employers following a wave of complaints that they are being employed in roles reserved for Thai nationals.
Minister Suchart Chomklin said he had instructed the Department of Employment to take action against those who break the law.
A campaign is also underway to educate Thai business operators and migrant workers about the job types which are reserved for Thai nationals only.
According to some media reports, migrant workers now take up jobs as street vendors, Thai massage therapists and hairdressers in Bangkok and neighbouring provinces.
Mr Suchart said food vending, traditional Thai massage and hair-dressing are off-limits to migrant workers.
Under the law, migrant workers are strictly banned from working in 27 professions and are allowed to work in 13 other professions under certain conditions.
Any found without a permit or doing jobs they are not allowed to are subject to fines of between 5,000 and 50,000 baht and sent back to their home countries.
Thai employers are liable to fines of up to 100,000 baht for every worker illegally employed. They will also be prohibited from hiring migrant workers for three years for repeat offenders, not to mention a one-year jail term and/or fines of up to 200,000 baht.
DoE director-general Pairoj Chotikasathien said officials have been monitoring the employment of migrant workers across the country to ensure compliance.
In the 2022 fiscal year, 918 migrant workers were rounded up for "stealing Thai people's jobs" amid inspections at 35,258 workplaces.