Abstract: On the basis of 32-year daily precipitation observation data from Thailand’s meteorological department during 1981–2012, using linear trend and EEMD (ensemble empirical mode decomposition), this study focused on the changes in the proportion of stations with abnormally high (95th percentile and above) precipitation and precipitation days in multiple grades in Thailand as a whole and its five geographical regions and further analyzed the annual precipitation and the variation trend of the relative contribution of annual persistent and nonpersistent precipitation to annual precipitation above heavy rain level. The main conclusions are as follows: (1) Annual precipitation is the strongest in eastern and southern Thailand and the weakest in northern Thailand. Additionally, during the 32-year study period, it shows an increasing trend at 87% of the stations (with 22 stations reaching the 90% confidence level), showing the fastest increase in South Thailand and the slowest increase in eastern Thailand. In Thailand, annual precipitation at the Bangkok and Nakhon Si Thammarat stations on the coast of the Gulf of Thailand shows the most significant increasing trend. (2) The proportion of stations with abnormally high annual precipitation, annual precipitation days, and mean precipitation intensity increase significantly in North Thailand, which indicates that the range of extreme precipitation is expanding, while in southern Thailand, only the range of extreme precipitation for precipitation above storm rain level increases significantly. (3) In Thailand, precipitation above heavy rain level varies significantly in different regions. In North, Northeast, and central Thailand, precipitation-heavy is more of a nonpersistent form, while in East and South Thailand, two forms (nonpersistent and persistent) of precipitation are balanced. The proportion of stations with abnormally high persistent precipitation above heavy rain level has a significant expansion trend in North and South Thailand, which indicates that the range of heavy precipitation under the influence of the stable system has a significant expansion trend.