The calculated distance (air line) between Kampong Speu and Siem Reap is approximately 139 miles respectively 224 kilometers.
By car or train, the actual journey to Siem Reap is certainly longer, as only the direct route (as the crow flies) between Kampong Speu and Siem Reap has been calculated here.
Air line (approximately)
224 kilometers
121 nautical miles