Thailand is easiest when you treat it as two destinations in one. The Andaman coast delivers the headline dives: offshore reefs, bigger structures, and boat itineraries that string together sites like Richelieu Rock and Koh Bon. The Gulf side, especially Koh Tao, is a training powerhouse with short rides to reefs and pinnacles like Sail Rock. Across the country you get warm water, approachable depths, and a mix of coral gardens, schooling fish, and occasional pelagics. Choose region by season, and match your goals: calm bays for fundamentals, then pinnacles and wrecks when you want challenge.

Thailand is a friendly freediving destination because water is warm, logistics are easy, and there is a big training community. The center of gravity is Koh Tao, where you can combine line training with relaxed snorkel-style exploration on days you want less structure. The Gulf generally offers more protected bays and short boat rides, while the Andaman side can be excellent in its calm season if you want clearer water and more dramatic scenery between sessions. Plan around monsoon exposure, prioritize boat traffic awareness, and choose operators that run conservative safety systems. Expect comfortable water, commonly around 28°C to 31°C, with the best sessions happening in lighter wind and smaller surface chop.

Thailand is excellent for snorkel-first trips because you can find clear, shallow water without complex logistics. The Gulf islands offer protected coves and sand-bottom entries, while the Andaman side shines when seas are calmer and offshore visibility improves. Build your days around sheltered bays, arrive early for glassier water, and use a flotation aid if anyone in your group is not a confident swimmer. In many places, great reef viewing starts in just 1 m to 3 m of water, and visibility can range from 10 m to 25 m on good days. Popular anchors include Aow Leuk, Koh Ma, and Andaman island stops like Koh Poda.

Thailand is one of the best dive trips for mixed groups because the surface interval can be a highlight, not a compromise. Between boat days you can switch from Bangkok street food and temples to jungle lake overnights, limestone cliffs, and beach towns with night markets. The same coastal bases that unlock great water time also unlock easy excursions: Phuket for viewpoints and bay kayaking, Krabi for limestone and lagoons, and the Gulf islands for short hikes and sunset beaches. Plan for heat and humidity in the warmer months, and pack for sudden rain showers in wet season. If you want the most comfortable sightseeing weather, the cooler months often feel best for long walks and big day trips.