The calculated distance (air line) between Sihanoukville and Svay Rieng is approximately 158 miles respectively 254 kilometers.
By car or train, the actual journey to Svay Rieng is certainly longer, as only the direct route (as the crow flies) between Sihanoukville and Svay Rieng has been calculated here.
Air line (approximately)
254 kilometers
137 nautical miles