The calculated distance (air line) between Vang Vieng and Ban Houayxay is approximately 162 miles respectively 260 kilometers.
By car or train, the actual journey to Ban Houayxay is certainly longer, as only the direct route (as the crow flies) between Vang Vieng and Ban Houayxay has been calculated here.
Air line (approximately)
260 kilometers
140 nautical miles