Songkhla Province is located on the eastern coast of the southern Thailand, between latitudes 6o17'-7o56' N and longitudes 100o01'-101o06' E. The province has two seasons, like Nakhon Si Thammarat, but the dry season is from February to the middle of July. Both areas experience the highest precipitation in November and the highest temperature in May. The total rainfall in 2013 was 2868. 6 mm in Nakhon Si Thammarat Province and 2793.6 mm in Songkhla Province and temperatures averaged about 27.94oC. Four out of seven areas in Nakhon Si Thammarat province were herbicide-use areas, the others are herbicide-non-use areas.