The calculated distance (air line) between Siem Reap and Stung Treng is approximately 142 miles respectively 229 kilometers.
By car or train, the actual journey to Stung Treng is certainly longer, as only the direct route (as the crow flies) between Siem Reap and Stung Treng has been calculated here.
Air line (approximately)
229 kilometers
123 nautical miles