The calculated distance (air line) between Mueang Nonthaburi and Si Racha is approximately 55 miles respectively 89 kilometers.
By car or train, the actual journey to Si Racha is certainly longer, as only the direct route (as the crow flies) between Mueang Nonthaburi and Si Racha has been calculated here.
Air line (approximately)
89 kilometers
48 nautical miles