After graduating, Thun worked with Ettore Sottsass and helped found the famous Memphis group, which revolutionized Italian design in the 1980s. In 1984, he opened his own design studio in Milan, where he worked on a variety of design projects, from interior architecture to furniture and consumer products.
Over the course of his career, Thun has worked for many renowned companies such as Alessi, Artemide, Fontana Arte, Swatch, and above all for the Radisson SAS hotel chain, for which he created a visual identity and interior design that quickly became iconic.
Thun has also taught design at a number of prestigious schools, including the Sorbonne University in Paris and the Domus Academy in Milan.
In addition to his design career, Thun is also an artist, and has exhibited his work in galleries around the world. In 2001, he was named Chevalier de l'Ordre des Arts et des Lettres by the French government for his work in design and art.