The calculated distance (air line) between Muang Xay and Luang Namtha is approximately 42 miles respectively 67 kilometers.
By car or train, the actual journey to Luang Namtha is certainly longer, as only the direct route (as the crow flies) between Muang Xay and Luang Namtha has been calculated here.
Air line (approximately)
67 kilometers
36 nautical miles