That is an EKW C-3603.
It was a Swiss multi-purpose combat aircraft of the 1930s and 1940s, built by the Eidgenoessische Konstruktionswerkstaette. It was a single-engined monoplane with a crew of two. It entered service in 1942, and despite being obsolete, remained in front line use until the early 1950s, and as a target tug until 1987.