The calculated distance (air line) between Khlong Luang and Suphan Buri is approximately 45 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 Khlong Luang and Suphan Buri has been calculated here.
Air line (approximately)
73 kilometers
39 nautical miles