The calculated distance (air line) between Luang Namtha and Ban Houayxay is approximately 79 miles respectively 127 kilometers.
By car or train, the actual journey to Ban Houayxay is certainly longer, as only the direct route (as the crow flies) between Luang Namtha and Ban Houayxay has been calculated here.
Air line (approximately)
127 kilometers
69 nautical miles