The owner wants to upgrade the 30 years old auto repair service building to be the headquarters of the new company, which sells spare parts for tractors, in Banthatthong road. The original building is the reinforced concrete structure. Inside the 5-story building, there is an open-air center, similar to a factory. The design approach is to keep the free space in the middle, and extend the outside of the first and second floor to be a bridge that connects the four sides of the wall into a meeting room. The area in the third and fourth floor will be a storage room, and the fifth floor is the residential area. The middle court brings the natural light inside the building, where the SKYLIGHT, the form that could create light and shadow inside the courtyard to imitate furrows of tractor wheel on the ground, will be used. The light and shadow will be changed by the direction of the light, depending on the time and season. Furthermore, the temperature will be lower than the outside by opening the vents to allow the heat to flow out through the roof, and replaced by the cool breeze from below. Hence, this could reduce the workload on air conditioning, particularly in the working area.