Best Time to Visit Bangkok
Recommended: Nov to Feb
When to go
November to February is cool season: 21-32°C, low humidity, minimal rain, and the best month by far is December-January. March-May turns brutally hot (up to 36°C). June-October is rainy season with short, heavy afternoon downpours and fewer tourists, which some people prefer for lower hotel prices.
Month by month in Thailand
Bangkok sits in Thailand, so the country's broader seasonal pattern applies. November to February is dry and cool almost everywhere and the closest thing to a universal answer. After that it splits by coast: the Andaman side and the Gulf side flood at different times of year.
Nov-FebCool and dry nationwide, the safest bet for Bangkok, Chiang Mai and both coasts. Also the most crowded and priciest.
Mar-AprHot season, temperatures spike into the high 30s. Songkran water festival mid-April is chaotic fun if you don't mind getting soaked.
May-OctSouthwest monsoon soaks the Andaman coast (Phuket, Krabi), wettest around Sept. The Gulf side (Koh Samui) stays comparatively dry through most of this window.
Oct-DecNortheast monsoon flips it: Koh Samui and the Gulf islands get their rain, peaking in November, while the Andaman coast dries out.