Twenty-four Myanmar and Tai Yai job seekers were arrested on Monday for illegal entry in Phitsanulok province.
Boonlua Maramee, deputy governor of Phitsanulok, said a team of immigration police and administrative officers spotted the 17 women and seven men as they were travelling to a factory in tambon Don Thong, Muang district.
The team was acting on a report that there were a group of migrants entering tambon Don Thong.
The factory owner initially claimed that the migrants legally entered the country but failed to provide substantial evidence, including work permits.
Initial health checks showed none of them had Covid-19.
They were to be deported after legal proceedings.
Border security has been beefed up in recent months to deter border crossers who might be transmitting the coronavirus. But illegal crossings remain frequent, especially from Myanmar where economic conditions have deteriorated considerably since the military seized power last February.
At least 68,000 illegal border crossers, the vast majority of them from Myanmar, were caught from January to November last year, estimated Adisorn Kerdmongkol, a representative of a migrant labour development network.
The monthly total jumped to 10,870 in November when the country reopened to tourism, and climbed further to 12,000 in December, he said, adding that as many as 100,000 had probably slipped past the authorities and were now employed in major provinces.