The calculated distance (air line) between Amnat Charoen and Udon Thani is approximately 163 miles respectively 262 kilometers.
By car or train, the actual journey to Udon Thani is certainly longer, as only the direct route (as the crow flies) between Amnat Charoen and Udon Thani has been calculated here.
Air line (approximately)
262 kilometers
141 nautical miles