The calculated distance (air line) between Frauenfeld and La Chaux-de-Fonds is approximately 102 miles respectively 164 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 Frauenfeld and La Chaux-de-Fonds has been calculated here.
Air line (approximately)
164 kilometers
89 nautical miles