The calculated distance (air line) between Thap Khlo and Udon Thani is approximately 169 miles respectively 272 kilometers.
By car or train, the actual journey to Udon Thani is certainly longer, as only the direct route (as the crow flies) between Thap Khlo and Udon Thani has been calculated here.
Air line (approximately)
272 kilometers
147 nautical miles