August is the Gulf coast's best month: Koh Samui, Phangan and Tao get calm seas and dry days while the Andaman is in full monsoon. Expect 30–33°C and short afternoon showers on the Gulf side.
The short version
- The best month for Samui, Phangan and Tao.
- Avoid Phuket, Krabi and Koh Lanta — boat trips are frequently cancelled.
- Mother's Day and the Queen's birthday on 12 August is a public holiday.
- Prices on the Gulf peak with European holidays; the Andaman is cheap and quiet.
Two coasts, opposite weather
The Gulf is at its best: calm water, sunny mornings, good visibility for diving. The Andaman is in the middle of the monsoon, with rough seas and frequent afternoon rain.
Holidays and crowds
12 August is Mother's Day and a long weekend, when Thai families travel — book accommodation ahead for that week. Otherwise August is quiet.
What to do
Dive or snorkel around Koh Tao, take a boat to Ang Thong, or head north for the hills, which are green and cool. Skip island-hopping on the Andaman.
Where to go in August
August is unambiguous: the Gulf. Koh Samui, Koh Phangan and Koh Tao have their best month, with calm seas, dry days and good diving visibility on the west coast of Tao. Book early, because European school holidays push Gulf prices to their annual peak.
The Andaman is in full monsoon. Khao Lak and the Similans are closed, Phi Phi boats are frequently cancelled, and the west-coast beaches have red flags. If you are already booked there, plan land-based days and take the good weather as a bonus rather than an expectation.
The north is a reasonable third option — wet but green, with the Mae Hong Son loop at its emptiest. The one thing August does not offer is a reliable beach on the Andaman, so do not book one.
