This building was made of three plaster layers of solid brick masonry with each layer, the building was painted in a light-yellow color. It was a Neoclassical architecture with a rectangular floor plan and a symmetrical building elevation plan, which was a simple “E” shaped plan. This building is designed to have a front porch on each floor, a stairway hall in the middle of the building, a staircase, and a restroom located on the side wings of the building.

      The building plan is symmetrical and has a total of three apses. The main entrance, located at the central apse: it has the car drop-off area and stairway hall. The central apse was a major vertical-to-horizontal circulation space center. The main staircase was specially designed to be divided into two flights (the imperial staircase) that branch off to the right and left and go around the staircase wall. After that, it returns to the next level of the hallway. Apart from that, the circulation space was a single-load corridor, resulting in the completely distinctive design patterns of the front elevation and rear elevation.

      A floor plan was designed as a modular system, which means each floor is comprised of only two sizes of a room. The room was constructed without a center column and a wide structure that allowed the architect to freely divide the space in each room. This modular system has an impact on the entire layout of the building's doors and window voids. For example, a large room consists of three wide window voids and five long window voids, while a small room consists of two wide window voids and three long window voids. These doors and window voids were all installed in exact positions, allowing the ventilation systems to be fully functional and creating a unified appearance for the buildings' interior and exterior.

      Tamagno “adapted” the front elevation to be different from the standard Neoclassical architecture; the elevation was intended to reflect the different hierarchy of the three-story building’s users
      The ground floor of this building--used as the officers' general office and the guest services organization--was designed to create a quiet stifling atmosphere and plastered with a groove line that resembles the rusticated base. The doors and window voids on the ground floor were all square-shaped. The walls between the voids were plastered, creating a groove line on the wall throughout the horizontal line of the building, which created the feeling of hardiness and stability.

      On the second floor were the minister’s and directors' offices. The room was designed with arched windows and decorated on the windowsill with a security bar with a baluster. This design brings about the vista of the second floor as the main floor of this building.
      The third floor was an executive's office, especially the position of advisor of the Ministry of Commerce. The room was designed as a simple square attic window.

      The building's rear elevation and side elevation
The rear of the Ministry of Commerce building was to the southwest, which was comprised of three-story office space. Due to the elevation that turned back toward the Government Laboratory building, this was the only side that the officers could see. The architect designed the building elevation totally differently from the front elevation. The front elevation of the building in terms of Neoclassical architecture was to create enormous and majestic feelings. But the architect has lessened the design of rear elevation, which has only one central apse. The window voids on the ground floor and the second floor were simple square shaped with the same dimensions. The similar design of a block of three windows throughout the third floor were installed with a cornice along the entablature located between the ground floor and the second floor. A cornice was installed at the eaves, which continually from the front elevation.

      The side elevation has dimensions of five-width blocks of columns and was designed to continue from two blocks of columns from the front elevation and three blocks of columns from the rear elevation, although there were contrasting components. The front elevation has a pilaster that extends beyond two interior stories. A pilaster has a horizontal fluted on the bottom. Many doors and windows have voids for decorations. On the other hand, the rear elevation has only a horizontal canopy on the window. Together with the specification designs that organized the range, they created the continuity of the entablature. Moreover, this side elevation design pointed out that the architect focused on the sense of a three-dimensional building. Consequently, the architect bended the side elevation and encircled all four building angles because of the diagonal layout of the road. Passengers on the Sanam Chai or Maharat roads can catch a glimpse of a building's corner rather than be confronted with a side elevation view.

      The Ministry of Commerce building demonstrates interior design ideas as well as the building’s exterior lookings. The designs have divided the space building into systematic working spaces that have access to natural light. The room has great ventilation, so there are few interior design elements inside the working space. The entire room’s floors were a tongue and groove joint. The walls were plastered and painted. The doors were teak wood, on the upper part of the doors was an awning shingle wooden panel to ventilate with no decorations. And the precast concrete ceiling that was installed on the precast concrete or wood slat ceiling was a coffered ceiling and tongue and groove which was set to the same construction standard in the building.

      A circulation space is located in the entrance hall, the stairway hall, and the hallway. This circulation space, which was specially designed as the main stair hall, is located at the central apse; it is a square room with a three-story building with window voids on three sides, which bring natural light indoors. The staircase offers a route between the first and third floor. It builds a support structure into the surrounding walls. This gives the impression that the staircase is floating without being supported by any column. The fourth side of a wall was the side that connected to working space and was the most decorated part of the building. It was divided into three blocks of columns; each block had a double-column to support the floor structure. On the middle column was an entrance to a working space, and the columns on either side had a railing decorated with turned stone bars of a window. The architect laid out a different order for each of the double-columns.

      A round Tuscan column style is located on the ground floor to support the building foundation.

      A round Ionic Scamozzi column capital is located on the second floor to support a short beam.

      A square coupled with columns with narrow tapering assembles the upside-down of the Obelisk order. These columns are one of the features of Baroque architecture. This complicated design has reflected variation of the building functions as well as the different heights of each floor.

      The concept of architectural values focuses on resurrecting the original conditions of the building, which was an office building. It was the first period of Siam that had a reinforced concrete structure building. The building conservation process had explored information and evidence that led to the understanding of original building’s functions in order to revive the original condition. The conservation encourages the audience to appreciate the original condition of the building in many ways: for instance, the preserve of wall color that was left as a small spot in each room; the wooden floor displayed in the exhibition room to show the complex technique of floor construction; the piping construction, the original septic tank and surge tank located at the front of the building. Due to the renovation process that restored original building materials and authentic decorations as much as possible, the architect avoided building extensions and the exhibition design that might affect the historical site as well as respected the primary technique and construction. This conservation is concerned with visitors' acknowledgements of the original building space, so there is no constructing of ceiling or installing durable goods in the position that would conceal the building elements and allow natural light to shine into some of the exhibition rooms.

      The concept of determining space utilization was originally designed to be an office building that could withstand its own weight. However, such design could not bear the weight of a museum with a large number of visitors. Given that, the architect solved such problem by selecting lightweight exhibit objects and durable goods as well as avoiding installing objects in the middle of a room. Although the main staircase was beautiful, it can bear less weight than the secondary staircases at the ends of the building, so the architect defined a suitable walking trail for an exhibition that starts from the secondary staircase on the left wing (Sanam Chai road) and walks to the third floor of the building, then walks down to the second floor by the secondary staircase on the right wing, and uses the main staircase only for walking down to the ground floor.

      The building's mechanical and electrical systems were installed with ventilation and air distribution systems in the original office room, which was part of an exhibition, by installing the water-cooled chiller system along the gap between two layers of brick walls and between the wooden joists on the ground. In this case, there is no need to build a shaft that would interfere the historical site. The architec installed a standing floor Fan Coil Unit (FCU) and cover it because the condensing unit was placed on the fence's rims, away from the building. All the space in the hallways and staircase were not installed with ventilation, so the walking trails for an exhibition were all located in the old working area where each room was connected. Besides, there was a full installation of the electrical system, the communication system, the fire alarm system, and the Closed-Circuit Television system (CCTV) by wiring in the U-shaped, which assembles to the old wiring methods, because of the special structures of the floor and walls in this building. There was no space above the ceiling to hide a wire. The plumbing system for the bathroom located on the side apse must be reinstalled without hiding in the walls and creating symbols to show the lines of the original one. A Fire Hose Cabinet (FHC) is installed so that the fire hose length meets the requirements of the building code. It is located at both stair landings.

      The concept of building conservation techniques.
      Due to the limited funds, the conservation process was necessary to use the original materials as much as possible. For example, a layer of plaster on a wall structure, doors and windows, and terrazzo tiles are still intact. If some substituted materials are required to be created, they must be in appropriate construction and cost saving at once. For instance, to create diamond slate roof tiling, red color is sprayed; to create tiled hallways around the building, a patterned paint roller is made-up to imitate pattern of the original tiles. Mostly, these constructions were composed of components manufactured in Thailand. They can be easily replaced, are good quality products, not too expensive, and have a low cost of maintenance.