Koh Samui weather is almost always beautiful. Blue sky days and a nice ocean breeze are the norm. For the purists, late December to the end of March is the ideal tropical island weather experience.
Some like it hot! If so, April to June is the time to really bake. Some like it wet! Try mid - October to early December.
Getting here is easy - just a short 80 minute flight from Bangkok, but literally a world away from the action packed streets of the capital city.