The calculated distance (air line) between Samut Prakan and Nakhon Pathom is approximately 40 miles respectively 65 kilometers.
By car or train, the actual journey to Nakhon Pathom is certainly longer, as only the direct route (as the crow flies) between Samut Prakan and Nakhon Pathom has been calculated here.
Air line (approximately)
65 kilometers
35 nautical miles