The rainfall variability of each season over Thailand was exhibited by the EOF technique. The most dominant mode of each season the variability accounts for 47.5%, 24.1%, 31.0% and 21.3% of the total variance respectively. It can explain the variation of the long term average of rainfall during the season of over Thailand. The correlation analysis suggests that the Nino3, the Nino3.4 SST index influence rainfall variability of each season over Thailand. Especially, the most correlation between the Niño3.4 with rainfall during March April and May (summer).