The largest grouping of Thai Infantry is the Division. There are eight infantry divisions. All share the same force structure as seen below.
Image from http://niehorster.orbat.com/082_thailand/43/div_inf.htm
Each Division consists of three regiments of Infantry, two Artillery battalions, a Communications battalion, a Medical battalion, and a dedicated Command company.
The eight Divisions are stationed as follows:
1st and 3rd: Along the border with British Burma
2nd and 5th: Along the border with French Indochina
4th: In and around Phucket
6th: Bangkok. This is the only division of Marines.
7th and 8th: Both of these divisions are reservists. There assembly areas are just outside of Bangkok.