The calculated distance (air line) between That Phanom and Maha Sarakham is approximately 107 miles respectively 172 kilometers.
By car or train, the actual journey to Maha Sarakham is certainly longer, as only the direct route (as the crow flies) between That Phanom and Maha Sarakham has been calculated here.
Air line (approximately)
172 kilometers
93 nautical miles