Light 4×4 trucks Model 50/51 of the Royal Thai Army.
The light 4×4 trucks Model 50/51 originated from the Royal Thai Army Ordnance Department's 2000 requirement for a 1/4-ton M151 light truck. Civilian vehicles available at the time—namely Toyota Tiger, Mitsubishi Strada, Isuzu, and Ford—were modified to produce the Model 50 light truck. Production was undertaken by Preecha Thaworn Industry Company, with orders totaling 727 units between 2008 and 2010, including additional parts worth 756.2 million baht.
Subsequently, the light truck Model 51 was developed with sub-models 51A, which uses the Mitsubishi Triton pickup chassis, and 51B, which uses chassis from Mitsubishi Triton, Toyota Hilux Vigo, and Revo pickups. Production was also by Preecha Thaworn Industry. The design was registered as a Thai invention, researched by the Army's Military Research and Development Office, and registered in 2016. Additionally, a medical version, the Model 51 ambulance, was produced.
In 2019, the Ordnance Department commissioned the production and assembly of Model 51 light 4×4 trucks in two versions: the 51A (command and machine gun mounting version) priced at 1,493,000 baht each for 58 units, and the updated 51B version at 1,366,000 baht each for 101 units. Also ordered were 27 units of the Model 51 4×4 ambulance (4 stretcher capacity) at 2,999,870 baht each. The winning bidder was S.S.S. Automotive Industry Company, with a quoted budget of 305,556,490,490 baht.
The light 4×4 trucks use a four-wheel-drive system with a 1/4-ton capacity. The vehicle chassis are based on Toyota Hilux, Mitsubishi, Isuzu, and Ford pickup trucks. The vehicles feature canvas roofs and lack interior air conditioning.
The subsequent 51A/B models evolved from Model 50 by replacing the canvas roof and lack of air conditioning with a steel roof and installed air conditioning. The doors are armored steel reinforced for bullet protection to safeguard occupants. Additionally, the Model 51 ambulance features a rigid steel roof frame and can accommodate up to four patients on stretchers.
The light 4×4 trucks use 7J-16 wheels with 750-16 or 265/75R-16 tires, equivalent to 8-ply rating, featuring tread patterns suitable for terrain use or lugged designs. They meet military standards set by the Ministry of Defense's Ordnance Standard Committee (G.M.Y. MoD).