Seismic source zones for Thailand was first introduced by Nutalaya et al. (1985), based upon both seismological and geological evidences. Subsequently, Shrestha (1990) identified 9 active faults in the country on the basis of only seismological data analysis. Recently Department of Mineral Resources put an enormous effort to produce the active fault map of Thailand (Fig. 1) with the co-operative research studies of Chulalongkorn University (Thailand) and Akita University (Japan) on the bases of all the relevant geotectonic, digitally - enhanced satellite-borne image, geochronological, historical and seismological data along with the earlier published works (e.g., Hinthong, 1995; Nutalaya et al., 1985). Apart from the above - mentioned information applied, the other significant data are from the results of morphotectonic trench log and geophysical investigations. This commences with remote sensing interpretation to determine significant lineaments, follows with Quaternary field mapping of landforms, and then identifying morphotectonic features and styles – including primary, as fault scarp degradation and secondary, such as offset and beheaded streams, sag ponds, shutter and pressure ridges. Then ground geophysic (resistivity and GPR) surveys are carried out to confirm the existence of the interpreted faults. Detailed geodetic survey has been performed in detail to locate the appropriate site for exploratory trenching. Detailed stratigraphic logging has been done prior to sampling for Quaternary dating have been made. Based upon these consecutive sequences of work, we can delineate the Fault Zone (FZ), which is herein defined as linear or elongate zone of seismicity commonly classified by neotectonic movement and coincident with major tectonic structures. As displayed in Fig. 1., Thailand consists of 15 active FZ. Followings are a summary of the faults that have been studied.