The cold season is generally from November to February. In the north of Thailand, say Chiang Mai and Chiang Rai, it might get cold enough that you’ll see frost. On a really windy cold night it might even get as low as 40F (or at least it will feel that cold). Although many of us foreigners vacation in Thailand to flee the winter in our home country, Thais like to travel to northern Thailand to experience what cold weather is like. Even frost on the grass is a white wonder winterland for them. I’ve never heard of snow or even hail in Thailand, The southern-most regions of Thailand generally don’t have a cold season.