The calculated distance (air line) between Frauenfeld and Biel/Bienne is approximately 83 miles respectively 133 kilometers.
By car or train, the actual journey to Biel/Bienne is certainly longer, as only the direct route (as the crow flies) between Frauenfeld and Biel/Bienne has been calculated here.
Air line (approximately)
133 kilometers
72 nautical miles