The calculated distance (air line) between Thun and La Chaux-de-Fonds is approximately 45 miles respectively 72 kilometers.
By car or train, the actual journey to La Chaux-de-Fonds is certainly longer, as only the direct route (as the crow flies) between Thun and La Chaux-de-Fonds has been calculated here.
Air line (approximately)
72 kilometers
39 nautical miles