Conversely, the STR had the highest errors, as the southern region receives relatively high and varied rainfall throughout the year but having correlation to SCSI and Niño indices. Thus, it is difficult to detect a clear relationship of rainfall and the considered indices extcolor{magenta}{in the southern Thailand}. The results of this research will contribute to a better understanding of rainfall variations in each region of Thailand. Furthermore, this finding would benefit people in each region of Thailand as well.