Phutthayotfa Chulalok-class frigate

The Phutthayotfa Chulalok class is the Royal Thai Navy's name for two frigates, HTMS Phutthayotfa Chulalok and HTMS Phutthaloetla Naphalai, which were originally United States Navy Knox-class ships, USS Truett and USS Ouellet. They were two of the forty-six Knox-class ships laid down as ocean escorts and redesignated frigates in the 1975 reclassification. Thailand leased and then bought them in the 1990s after the American navy retired them, and the ex-Ouellet received a refit at Cascade General Shipyard in Portland, Oregon before sailing for Thailand. The ships are about 134 metres long and are powered by a single geared steam turbine fed by two boilers, rated at 35,000 shaft horsepower for a speed of 27 knots. They were originally armed with a 5-inch gun, an ASROC launcher and torpedo tubes, and carried a helicopter deck and hangar. The Knox ships behind this class were built at Avondale Shipyards in Louisiana, and Thailand retired the pair after about two decades of service.