More than 3,000 migrants have been caught working without a permit as authorities crack down on those employed in jobs prohibited for foreign workers, according to the Department of Employment.
From October last year to Monday, the department randomly inspected 53,732 workplaces which hire migrant workers nationwide.
The agency found 3,464 migrant workers were employed without a permit.
Of them, 1,850 were from Myanmar, 636 from Cambodia, 562 from Lao, 145 from Vietnam and the rest from other countries. Also, another 1,634 workers were doing jobs prohibited for migrants.
Pairoj Chotikasathien, the department director-general, said 40 jobs are barred from being offered to migrants. Among the 40 off-limit jobs are hawkers, barbers, public transport services, massage therapists and tour guides.
Mr Pairoj said most migrants without permits and those in prohibited jobs were found in Bangkok and the major provinces of Nonthaburi, Chiang Mai, Chon Buri, Nakhon Pathom and Ranong.
Migrants found working in the 40 prohibited jobs face a fine ranging from 5,000 to 50,000 baht.
They will also be deported back to their home country and have a two-year employment ban in Thailand.