The calculated distance (air line) between Tuen Mun San Hui and Dongguan is approximately 45 miles respectively 73 kilometers.
By car or train, the actual journey to Dongguan is certainly longer, as only the direct route (as the crow flies) between Tuen Mun San Hui and Dongguan has been calculated here.
Air line (approximately)
73 kilometers
39 nautical miles