The most dominant mode in the EOF analysis of the seasonal September October November(SON) rainfall anomalies over Thailand. The proportion of variability in first mode it accounts for 21.3% of the total variance. The left figure show eigenvector and In the right figure show principal component time series in SON the first mode show that the relation of the eigenvectors is negative over the southern part near by Malaysia. But it is positive over at the most area of Thailand. The values of standardized(PC’s), it was found that there was the most negative in 1964 found that It was high rainfall in the southern part near by Malaysia. On the contrary, there was the most positive in 2002 found that, low rainfall in this area.