The contract, worth nearly $6 million, follows in-country trials of the systems with the Thai army.
Deliveries of an initial 42 TSS systems and the Surveillance, Target Acquisition and Weapon sight systems will start in February for use by the army in mid-2012.
The complete TSS system comprises the STAWS, a commander's display and a gunner's display. Integrated aiming software uses the laser-sighting capability of the STAW system to automatically elevate the tank's turret to the correct level, based on the range of the target and the ammunition type being used.
"The TSS is a cost-effective upgrade to legacy vehicles such as the Scorpion," Colin Horner, head of Campaigns Land ISTAR and Imagers at Selex, said. "It can provide extended direct fire capability to artillery platforms such as 155mm howitzers."
Selex's STAW sight system is a multi-waveband imaging solution used by the British army and other coalition forces on remote weapon stations and is well suited to the Scorpion light tank, he said.
The contract is within the first part of the Thai army's three-stage upgrade program that includes several other vehicles.
A statement by the U.K. Trade and Investment Department in July said the Thai army had selected a "British package" to upgrade its fleet of more than 150 tracked combat and reconnaissance vehicles, mostly consisting of Scorpions.
"So intense was the competition that the process went through several rebids before a winner was declared," the statement said.
The contract value is around $126 million and benefits U.K. companies such as Selex, Cummins UK and David Brown Gears.
The Thai army bought its Scorpions between 1973 and 1976.
The vehicles were made by Alvis, which was acquired by BAE Systems in 2004. Alvis became BAE Systems Land Systems (Weapons and Vehicles), now part of the BAE Systems Land and Armaments operating group.
Selex Galileo, a Finmeccanica company with headquarters in the United Kingdom, announced in January it is supplying an unidentified, non-NATO country with acoustic systems to locate enemy weapons.
The order for two Hostile Artillery Location systems is worth $7.2 million. No other contract details were given.
HALO is an acoustic weapon locating system that detects sound waves generated by gun or mortar fire and other explosions and uses data processing techniques to accurately determine the location of the source of the sounds.
It uses unmanned sensor posts -- with clusters of sensitive microphones -- to detect the pressure waves, the company said.