Need to know what you can more or less expect from the weather in Khao Lak and when is the best time to visit? The area's tropical climate guarantees warm weather all year round with the only thing changing being the amount of precipitation. The wet months sees low hotel prices and though the rainy season is avoided by some it is rare that you will be stuck in your hotel room for a full day. You will have plenty of sunshine for a great holiday and is guaranteed to benefit from the freshness showers bring.
November to April see very little if any rain and temperatures vary between 24 and 32 degrees Celsius. Of this whole period, hotel prices in April will be lowest and special deals available. From December until end January is peak tourist season seeing the highest hotel prices of the year. November, February and March is "shoulder season" with inter-mediate accommodation prices.
April and May is the hottest months with temperatures varying between 27 and 36 degrees Celsius. From June to October the south western monsoon blows onto southern Thailand bringing with it rain and cooler conditions as well as the cheapest hotel prices. You can still expect most days to be sunny with moderate temperatures.
The sea is rougher during this time which could cause boat trips to be postponed or canceled. If your plan is to go island hopping or a scuba diver hoping for clear under water visibility this might not be the best time. Temperatures between 20 and 30 degrees Celsius can be expected during this time.