The calculated distance (air line) between Tuen Mun San Hui and Kai Tak is approximately 15 miles respectively 24 kilometers.
By car or train, the actual journey to Kai Tak is certainly longer, as only the direct route (as the crow flies) between Tuen Mun San Hui and Kai Tak has been calculated here.
Air line (approximately)
24 kilometers
13 nautical miles