This study analyzed the dominant modes of rainfall data (APHRODITE data) in Thailand for period from 1951 to 2007 and the monthly rainfall data over Thailand are taken from Thai meteorological department 26 station. These data no missing values are in period from 1971 to 2012. The rainfalls data were applied to analyses for four seasonal averages that separate into DJF (December to February), MAM (March to May), JJA (June to April) and SON (September to November). The empirical orthogonal function (EOF) technique was employed.
The next part was study of relationship between ENSO using the sea surface temperature (SST) the Niño3 index with principal component time series (PC’s) of the most dominant mode each season and the Niño3.4 SST index with PC’s of most dominant mode each season. The Pearson’s correlation was employed. It was found that the Niño3.4 SST index was the most related to the MAM for both of rainfall data.