The calculated distance (air line) between Kowloon and Tuen Mun San Hui is approximately 14 miles respectively 23 kilometers.
By car or train, the actual journey to Tuen Mun San Hui is certainly longer, as only the direct route (as the crow flies) between Kowloon and Tuen Mun San Hui has been calculated here.
Air line (approximately)
23 kilometers
13 nautical miles