Phutthayotfa Chulalok-class frigate

Lead ship of the class, HTMS Phutthayotfa Chulalok in 2005
Class overview
Builders	Avondale Shipyards, Westwego, Louisiana
Operators	United States Navy ex-Knox-class frigate  Royal Thai Navy
Preceded by	Chao Phraya class
Succeeded by	Naresuan class
Built	1969–1974
In commission	1994–2017
Retired	2
Preserved	1
General characteristics
Type	Frigate
Displacement	4,065 long tons (4,130 t) (standard) 4,260 long tons (4,328 t) (full load)
Length	438 ft (134 m) loa 415 ft (126 m) wl
Beam	46 ft 9 in (14.25 m)
Draft	24 ft 9 in (7.54 m)
Installed power	2 × 1,200 psi (8,300 kPa) boilers 35,000 shp (26,099 kW)
Propulsion	1 × geared steam turbine 1 × shaft
Speed	27 kn (50 km/h; 31 mph)
Complement	250 officers and enlisted
Sensors and processing systems	SPS-40B 2-D air search radar SPG-53 fire control radar SQS-26CX bow sonar SQR-18 towed sonar SLQ-32(V)1 passive intercept
Armament	1 × 5"/54 caliber Mark 45 gun 1 × 20 mm Phalanx CIWS 8 × ASROC anti-submarine missiles 4 × Harpoon missiles 4 × Mk.32 torpedo tubes with Mark 44 torpedoes
Aviation facilities	Helicopter deck and hangar

The Phutthayotfa Chulalok-class frigates are two of forty-six Knox-class frigates originally laid down for the United States Navy as ocean escorts (formerly called destroyer escorts), but were all redesignated as frigates on 30 June 1975, in the USN 1975 ship reclassification and their hull designation changed from DE to FF. The Thai Navy acquired them between 1994 and 1996.