The calculated distance (air line) between Nakhon Nayok and Chanthaburi is approximately 125 miles respectively 202 kilometers.
By car or train, the actual journey to Chanthaburi is certainly longer, as only the direct route (as the crow flies) between Nakhon Nayok and Chanthaburi has been calculated here.
Air line (approximately)
202 kilometers
109 nautical miles