HTMS Khamronsin was returning to base from a patrol with the Royal Malay-sian Navy when it came across three Vietnamese trawlers with 15 crew near Koh Losin in Pattani at 11pm Monday.
At 1.30am, the Tor 97 patrol boat brought two trawlers with 13 crew to the base after they were caught near Koh Kra in Nakhon Si Thammarat.
All crews were charged with violating Thai fishing laws and given to Muang Songkhla Police.