The calculated distance (air line) between Zürich (Kreis 3) / Sihlfeld and Thun is approximately 60 miles respectively 97 kilometers.
By car or train, the actual journey to Thun is certainly longer, as only the direct route (as the crow flies) between Zürich (Kreis 3) / Sihlfeld and Thun has been calculated here.
Air line (approximately)
97 kilometers
52 nautical miles