In the view of tectonic setting of Southeast Asia, the coastal area of Thailand is a geologically stable region, the so-called Sundaland, where it has only the experience of very slow vertical crustal movement. Faults are the main geological structure that related to the coastal zone and they are believed to be tentatively active. The first is Three Pagoda fault trending NW-SE direction, and extending from western mountain range of Thai-Burmese border to the Western Gulf of Thailand coast. Ranong and Khlong Marui fault zone are the other two tentatively active faults trending NE-SW direction, extending from Andaman Sea coast offset the upland of southern Thai peninsula to the Gulf of Thailand coast. These faults are shaping the landform on the upper Gulf of Thailand coast, and southern Thai peninsula.