1. The central: the terrain is mostly flat and some province adjoining the sea gulf. Including 25 provinces.
2. The north: the terrain is mostly hills and valleys. Including 17 provinces.
3. The northeast: the terrain is mainly plateau. Include 20 provinces.
4. The southern: the terrain flanked by the sea. The left side on the Andaman Sea and the right side on the sea gulf. Including 14 provinces.