The calculated distance (air line) between Al Başrah al Qadīmah and As Samawah is approximately 160 miles respectively 258 kilometers.
By car or train, the actual journey to As Samawah is certainly longer, as only the direct route (as the crow flies) between Al Başrah al Qadīmah and As Samawah has been calculated here.
Air line (approximately)
258 kilometers
139 nautical miles