In March 2011, the Royal Thai Army had placed an order for 49 T-84/Oplot-T MBTs from Ukroboronprom. State Administration of Industrial Security Ukraine. The tanks were to be manufactured at the Malyshev plant based in Kharkiv, Ukraine, to replace its fleet of aging American M41A3 Walker Bulldog light tanks, dating from the Vietnam war era. The Oplot-T is an Oplot-M (export version) with some minor modifications to meet local requirements, such as different radio, air conditioner and so on. The Thai government had approved 7.155 billion baht ($227.7 Mn) to purchase the first 49 Oplot tanks
The Royal Thai Army has received 31 T-84 Oplot-T and an additional 5 were expected in November 2017. In March 2011, the Royal Thai Army placed an order for 49 T-84s to replace its fleet of aging M41A3 Walker Bulldog light tanks. The government has approved 7.155 billion baht to purchase the first 49 Oplot tanks to be assigned to several units: the 2nd Cavalry battalion (Royal Guard at Fort Chakrabongse, Prachinburi), the 4th Cavalry battalion (Royal Guard at Kiakkai, Bangkok), the 8th Cavalry battalion (Fort Suranari, Nakhon Ratchasima), and the 9th Cavalry battalion (Fort Ekathotsarot, Phitsanuloke).
In April 2017, it was reported that following the delayed deliveries from this tank, the Royal Thai Army had declined the remainder of the sale and acquired the Chinese VT-4 main battle tank instead of the Ukrainian tank, due to the long term delivery schedule. The signed order for 49 units has to be completed by the month of January, 2017, it was reported that other deliveries may not be expected. A 26 March 2018 press release by Ukroboronprom stated that the 2011 contract for supplying Oplot-T tanks to Thailand had successfully completed and that the last party of tanks had passed checks by the customers and would be sent to the buyer in the near future.
The T-84 is a Ukrainian main battle tank (MBT), a development of the Soviet T-80 main battle tank introduced in 1976. The T-84 was first built in 1994 and entered service in the Ukrainian Armed Forces in 1999. The T-84 is based on the diesel-engined T-80 version, the T-80UD. Its high-performance opposed-piston engine makes it one of the fastest MBTs in the world, with a power-to-weight ratio of about 26 horsepower per tonne (19 kW/t). The T-84 Oplot is an advanced version incorporating an armoured ammunition compartment in a new turret bustle; ten of these entered Ukrainian service in 2001. The T-84-120 Yatagan is a prototype model intended for export, mounting a 120 mm gun capable of firing standard NATO ammunition and guided missiles.