The calculated distance (air line) between Savannakhet and Nakhon Phanom is approximately 58 miles respectively 93 kilometers.
By car or train, the actual journey to Nakhon Phanom is certainly longer, as only the direct route (as the crow flies) between Savannakhet and Nakhon Phanom has been calculated here.
Air line (approximately)
93 kilometers
50 nautical miles