The calculated distance (air line) between Thái Nguyên and Cao Bằng is approximately 79 miles respectively 126 kilometers.
By car or train, the actual journey to Cao Bằng is certainly longer, as only the direct route (as the crow flies) between Thái Nguyên and Cao Bằng has been calculated here.
Air line (approximately)
126 kilometers
68 nautical miles