The calculated distance (air line) between Phetchaburi and Nakhon Pathom is approximately 49 miles respectively 79 kilometers.
By car or train, the actual journey to Nakhon Pathom is certainly longer, as only the direct route (as the crow flies) between Phetchaburi and Nakhon Pathom has been calculated here.
Air line (approximately)
79 kilometers
43 nautical miles