The calculated distance (air line) between Bo Phloi and Krathum Baen is approximately 68 miles respectively 110 kilometers.
By car or train, the actual journey to Krathum Baen is certainly longer, as only the direct route (as the crow flies) between Bo Phloi and Krathum Baen has been calculated here.
Air line (approximately)
110 kilometers
59 nautical miles