The calculated distance (air line) between Smach Mean Chey and Phnom Penh is approximately 127 miles respectively 205 kilometers.
By car or train, the actual journey to Phnom Penh is certainly longer, as only the direct route (as the crow flies) between Smach Mean Chey and Phnom Penh has been calculated here.
Air line (approximately)
205 kilometers
111 nautical miles