In December 2013, Thai shipbuilder Marsun Company Limited first announced that it had been awarded the contract to build the 58 meter vessel. While the RTN and Marsun have had an established partnership, the M58 is largest patrol boat the RTN has ever ordered from the company. This new class of Patrol Boat is expected to replace Huahin class ships: HTMS Huahin (541), HTMS Klang (542) and HTMS Sriracha (543), which were built by Asian Marine Services and Royal Thai Naval Dockyard. In August 2016, Marsun disclosed that the first M58 patrol boat, Leamsing (561), had been launched at the RTN-owned Thonburi Naval Dockyard in Bangkok.
The Leamsing (561) M58 Patrol Gun Boat type had a lenght of 58 meters and top speed of 24 knots. It is armed with a 76mm Oto Melara (compact variant) main gun, one 30mm cannon from MSI Defence and two .50 cal machine guns. Thales is likely to supply its TACTICOS combat management system as well as its MIRADOR optronic system. It has a length of 58 meters, a range of 2,500 nautical miles, a maximum speed of more than 24 knots, and a full-load displacement of 520 tons. Thales is likely to supply its TACTICOS combat management system as well as its MIRADOR optronic system.
The vessels are usually used for activities such as law enforcement, preventing infiltration in sea or onshore, protecting commercial and fishing boats, and carrying out search and rescue missions. According to the Navy’s Strategic Plan 2008 â€“ 2017 Royal Thai Navy will add this series with another three boat.