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