The calculated distance (air line) between Prachuap Khiri Khan and Krathum Baen is approximately 131 miles respectively 210 kilometers.
By car or train, the actual journey to Krathum Baen is certainly longer, as only the direct route (as the crow flies) between Prachuap Khiri Khan and Krathum Baen has been calculated here.
Air line (approximately)
210 kilometers
113 nautical miles