The calculated distance (air line) between Stung Treng and Phnom Penh is approximately 153 miles respectively 246 kilometers.
By car or train, the actual journey to Phnom Penh is certainly longer, as only the direct route (as the crow flies) between Stung Treng and Phnom Penh has been calculated here.
Air line (approximately)
246 kilometers
133 nautical miles