The calculated distance (air line) between Thái Nguyên and Dien Bien Phu is approximately 182 miles respectively 293 kilometers.
By car or train, the actual journey to Dien Bien Phu is certainly longer, as only the direct route (as the crow flies) between Thái Nguyên and Dien Bien Phu has been calculated here.
Air line (approximately)
293 kilometers
158 nautical miles