The understructure of Pasan reveals the complex engineering of interlocking steel and concrete beams that form its signature curved silhouette. The elevated design is strategically built to accommodate seasonal flooding, a characteristic of Nakhon Sawan's geography, while simultaneously creating a shaded multi-purpose plaza for visitors. The crisscrossing lines of the structure produce an intriguing play of light and shadow, transforming the undercroft into an airy, semi-outdoor gallery that showcases both artistic beauty and structural resilience.