Koh Samui tide times

Spring tidal range at Koh Samui runs 2.0 to 2.5 m above Chart Datum; neap range drops to 0.5 to 0.8 m. The regime is mixed diurnal — on most days outside the equinox periods, there is one dominant tide cycle per 24 hours rather than two equal cycles. At Chaweng Beach the practical effect is visible: at high spring water the beach narrows to 15–25 m of dry sand in the mid-sections; at low spring the same area widens to 50–70 m as the tidal flat exposes. During neap tides in the Gulf summer (May–August), the daily swing can drop to under 0.5 m, making the tidal state nearly irrelevant to beach users. For any activity sensitive to precise water depth — snorkelling reef flats, launching kayaks over shallow sand bars — check the predicted low-water height before heading out.

Koh Tan lies 5 km south of Koh Samui's Taling Ngam beach on the west coast. The reef flat on Koh Tan's north side is the main snorkel area; at low spring tide (which at Samui can reach as low as 0.1–0.2 m above Chart Datum) the flat sits under 0.3 m of water — uncomfortable snorkelling, with fins brushing coral. The best window is the two hours either side of high water, when the flat holds 1.0–1.5 m and water clarity is highest before the ebbing current resuspends sediment. Check the predicted high-water time on this page; the mixed diurnal regime means there may be only one high per day. Boat transfers from Taling Ngam or Ban Hua Thanon take 15–20 minutes.

The NE monsoon runs November through January and drives the dominant swell toward the east-facing coast — Chaweng, Lamai, and Ban Mae Nam in the north. During peak NE season, wind-generated swell at Chaweng can reach 0.5–1.5 m on sustained northeast winds, producing choppy or broken water at the beach. The combination of monsoon swell with a spring high tide produces the narrowest, roughest beach conditions of the year. Conversely, the west coast (Na Thon, Taling Ngam) is sheltered from the NE monsoon and usually calm during November–January. Koh Pha-ngan and Koh Tao to the north provide partial shelter for Samui's northernmost beaches. The southwest monsoon (May–October) reverses the exposure: the west coast takes the weather and the east coast is calmer.

Na Thon pier on Koh Samui's west coast is built to operate across the full tidal range. The vehicle and passenger ferry services to Donsak pier on the mainland (80 km, approximately 1.5 hours) are not tide-restricted under normal conditions. The ferry schedule is published by Seatran and Raja Ferry; suspensions occur during SW monsoon weather (May–October) when winds and swell exceed operational limits — this is a weather restriction, not a tidal one. The highest tidal sensitivity in the Na Thon area is the approach channel for smaller vessels and longtail boats; at low spring, shallow-draft vessels must time their entry. Tide predictions on this page are from Open-Meteo Marine, ±45 min / ±0.2–0.3 m; cross-reference with TMD tide tables for vessel scheduling.

The predictions on this page come from Open-Meteo Marine, a free gridded global ocean model that estimates tidal height across a geographic grid rather than from harmonic analysis of a local gauge. Accuracy is typically within ±45 minutes on timing and ±0.2–0.3 m on height — adequate for beach planning and activity windows, but not for navigation or vessel berthing. The authoritative reference for Thai coastal waters is the Thai Meteorological Department (TMD), which publishes official tide tables and monsoon forecasts. For any safety-critical decision on the water, use TMD data. For general beach planning, the predictions here are sufficient as a starting point.