The calculated distance (air line) between Nong Phai and Udon Thani is approximately 151 miles respectively 243 kilometers.
By car or train, the actual journey to Udon Thani is certainly longer, as only the direct route (as the crow flies) between Nong Phai and Udon Thani has been calculated here.
Air line (approximately)
243 kilometers
131 nautical miles