Moreover, selected Drought Index values that were also related to the accumulated rainfall depth within each year at 14 sub-catchments in the UPRB that are the most reliable in assessing drought Basin in Thailand. The results showed that the lowest average monthly NMDI in February means 0.408 and increasing until highest average monthly in July means 0.545. NMDI is minor change values until August and then NMDI is decreasing until lowest average monthly NMDI in February.