Originally Posted by
MikeFromTokyo

Surely you are mistaken. December-February is the high season anywhere in South Thailand.
Really? Samui high season is when it rains the most? Surely it is you who are mistaken.
The best weather for the Samui group of islands is June-September. This is when the local hoteliers expect to be at their fullest. Isn't that the definition of high season?
You also might note that the monsoonal patterns for the Andaman coast and the east coast are different.