The arrests came on Thursday after police raided the factory in Ban Bung District, around 70 kilometers from Bangkok, after receiving a tip-off from locals that some Chinese managers working there did not have proper paperwork, Bangkok Post reported.
When asked to furnish work permits, the six could not. They had entered the country on tourist visas.
The six, aged 35-47, were handed over to the police station for working without proper permission.
Thailand, which has witnessed a strong recovery in tourism since late last year, is cracking down on people who overstay their visa and work illegally.
It received 11 million foreign visitors last year, and the government is eyeing 30 million arrivals this year.