While the impact on employment remains unclear, many workers could lose their jobs, Supant Mongkolsuthree, chairman of The Federation of Thai Industries, told the briefing.
On Sunday, it confirmed 315 new coronavirus cases, the majority of which are local transmission, bringing its total to 7,694 cases and 64 deaths since its first case last January.
Around half the 72 locally transmitted cases reported were linked to an outbreak discovered at the weekend at a seafood centre near the capital Bangkok, the ministry said in a statement.
The majority of the new cases are workers from Myanmar, who toil on shrimp boats and in processing factories linked to the multi-billion-dollar Thai seafood industry.
The new cases include 397 migrant workers in the southwestern province of Samut Sakhon, where Thailand's coronavirus worst outbreak yet was confirmed at the weekend.
On Monday Prayut blamed the outbreak on factories employing illegal migrant workers, who he accused of illegally crossing the porous Myanmar-Thailand border.
The outbreak appeared in Samut Sakhon province, southwest of Bangkok, where four infections were reported at a shrimp market on Friday.
Disease Control Department director-general Opas Karnkawinpong told a news conference that 516 new cases were found after testing that included 1,192 migrant workers.
The comment came after Washington put Thailand on its watch list of countries suspected of taking measures to weaken their currencies against the dollar.