The calculated distance (air line) between Nakhon Phanom and Huai Mek is approximately 117 miles respectively 188 kilometers.
By car or train, the actual journey to Huai Mek is certainly longer, as only the direct route (as the crow flies) between Nakhon Phanom and Huai Mek has been calculated here.
Air line (approximately)
188 kilometers
101 nautical miles