The calculated distance (air line) between Nakhon Pathom and Suphan Buri is approximately 46 miles respectively 73 kilometers.
By car or train, the actual journey to Suphan Buri is certainly longer, as only the direct route (as the crow flies) between Nakhon Pathom and Suphan Buri has been calculated here.
Air line (approximately)
73 kilometers
40 nautical miles