Prasart Kemaprasit, Rayong immigration police commander, said the nine fishing boats were delivering squid to Thai traders in the provincial seat.
The Vietnamese and Cambodians on board did not carry passports, travel documents or work permits. They told police that they left Vietnam six days ago and entered Thailand via Cambodia.
They said they caught squid in Klong Yai district of Trat province to Rayong before delivering the seafood to traders at the pier in the municipality.
They were charged with illegally fishing in Thai territorial waters.