The calculated distance (air line) between Phanat Nikhom and Samut Prakan is approximately 41 miles respectively 66 kilometers.
By car or train, the actual journey to Samut Prakan is certainly longer, as only the direct route (as the crow flies) between Phanat Nikhom and Samut Prakan has been calculated here.
Air line (approximately)
66 kilometers
35 nautical miles