This research aims to expend knowledge of the mechanism of slowly dissipating typhoons which are called “the long-lived typhoon” over Indochina. We analyzed the landing position of typhoons and decadal and monthly change in typhoon lifetime from 1958 to 2016. The typhoon lifetime seems to be related to landing position. The Self-Organizing Map (SOM)was used for classification based on the environmental field of precipitable water, wind velocity at 850hPa and sea level barometric pressure . The SOM result shows that the condition where the positive deviation field of precipitable water exists in the whole peninsula or the south part might cause long-lived typhoons.