Why Your Travel Month Decides Andaman Coast vs. Gulf of Thailand
Thailand has two opposite island weather regimes: from November to April, the Andaman Sea (Phuket, Krabi, Railay, Koh Phi Phi, Koh Lanta, Koh Lipe, Similan Islands) enjoys calm turquoise water. From May to September, when the Andaman gets southwest monsoon swells, the Lower Gulf islands (Koh Samui, Koh Phangan, Koh Tao) are sheltered and sunny until their brief October–November northeast monsoon.