May sees a welcome drop in temperature throughout the country, although highs of 33-34°C are not unusual, and most (but not all) regions experience a notable rise in rainfall, albeit low and sporadic initially.
Khao Sok National Park is warm and wet in May, with high levels of humidity. The islands of Koh Chang and Koh Kood are particularly wet during May and there is a high chance of rain on the west coast beaches of Phuket, Khao Lak and Krabi. For guaranteed sunshine, Hua Hin & Cha Am and the east coast beaches of Koh Samui, Khanom and Koh Pha Ngan are the pick of the bunch, with little, if any, rain expected.
Despite the possibility of rain, May is a great month to visit Thailand as plenty of sunshine is still expected and the visitor numbers are far lower than in previous months.