The Gulf of Siam
The Gulf of Thailand is, in the winter season, between November and March an area where you can count on steady winds of 15-30 knots. This time of the year there is the most agreeable climate, too, with temperatures of 24-35 C.
 
From April to mid June the hot season (up to 40 C ) follows, with still steady winds. Then the raining season is coming from July to end of October, with very calm up to stormy winds.
You rarely find winds with speeds over 50 knots and there is almost no chance that you are hit by a typhoon.

Two areas present themselves as ideal place to enjoy your holidays on a sailboat.

First, the islands Ko Samui, Ko Pangnan, Ko Tao and the National Park Ang Thong.

Second, the sea off Pattaya with the islands Ko Lan, Ko Phai, Ko Khram, Ko Samet and the sea off Trat, including Ko Kut, Ko Mak, and Thailand's second largest island, Ko Chang.
 
Pattaya     Ko Chang     Ko Samui