The calculated distance (air line) between Samdrup Jongkhar and Trongsa is approximately 78 miles respectively 126 kilometers.
By car or train, the actual journey to Trongsa is certainly longer, as only the direct route (as the crow flies) between Samdrup Jongkhar and Trongsa has been calculated here.
Air line (approximately)
126 kilometers
68 nautical miles