The calculated distance (air line) between Siem Reap and Kampong Cham is approximately 144 miles respectively 231 kilometers.
By car or train, the actual journey to Kampong Cham is certainly longer, as only the direct route (as the crow flies) between Siem Reap and Kampong Cham has been calculated here.
Air line (approximately)
231 kilometers
125 nautical miles