We conducted probabilistic seismic hazard analysis for Thailand and adjacent areas using a method proposed by Cornell (1968). We produced seismic hazard maps showing peak ground acceleration (PGA). Twenty-one seismic source zones covering all of Thailand and extend into adjacent areas were employed. The seismicity data used in this study was a merged data set covering 1963 - 2007 from several international earthquake catalogues and a single Thai catalogue. We selected the strong ground-motion attenuation model for this study by applying several existing attenuation models to recorded strong ground-motion data and choosing the model that best fit our data. Seismic hazard analysis was carried out for 2521 grid points on a 0.25° × 0.25° mesh within a rectangle defined by longitudes 92 - 106°E and latitudes 0° - 21°N. The resulting PGA maps for a 2% probability of exceedance for a 50-year time period suggest that ground motion of 0.3 to 0.4 g may occur in northern and western Thailand and from 0 to 0.2 g in other parts of Thailand. The seismic hazard analysis presented here is an important step toward an accurate evaluation of a seismic hazard potential in Thailand and adjacent areas. Further work is needed to refine the analysis. More observations of strong ground motion in the region are needed and further seismo-tectonic research should be encouraged.