In this study EOF it was found that the most dominant mode in the EOF analysis of the seasonal DJF, MAM, JJA, and SON rainfall anomalies over Thailand during 1951 to 2007 accounts for 47.5%, 24.1% , 31.0% , and 21.3% relatively of the total variance. Figure 1 shows the spatial pattern of the most dominant mode of (a) DJF, (b) MAM, (c) JJA, and (d) SON and figure 2 shows the temporal variation of this mode. Since the values in the spatial pattern are strongly positive over most of Thailand of (e) DJF, (f) MAM, (g) JJA, and (h) SON, it follows that when the principal component (PC) in the time series is positive most of Thailand has higher than normal rainfall, and when the PC is negative most of Thailand has lower than normal rainfall.