The calculated distance (air line) between Tai Mong Tsai and Mong Kok is approximately 10 miles respectively 16 kilometers.
By car or train, the actual journey to Mong Kok is certainly longer, as only the direct route (as the crow flies) between Tai Mong Tsai and Mong Kok has been calculated here.
Air line (approximately)
16 kilometers
9 nautical miles