The calculated distance (air line) between Khon Kaen and Nakhon Sawan is approximately 186 miles respectively 300 kilometers.
By car or train, the actual journey to Nakhon Sawan is certainly longer, as only the direct route (as the crow flies) between Khon Kaen and Nakhon Sawan has been calculated here.
Air line (approximately)
300 kilometers
162 nautical miles