The calculated distance (air line) between Samut Prakan and Krathum Baen is approximately 23 miles respectively 37 kilometers.
By car or train, the actual journey to Krathum Baen is certainly longer, as only the direct route (as the crow flies) between Samut Prakan and Krathum Baen has been calculated here.
Air line (approximately)
37 kilometers
20 nautical miles