Bangkok's heat rules out sustained outdoor activity between roughly ten and four. Locals structure their days around this; visitors frequently do not, and lose the outdoors entirely as a result.
Bang Krachao
The best outdoor half day in Bangkok.
An undeveloped green peninsula in a bend of the river, reached by a ten-minute boat from Klong Toey pier.
Bicycles hired at the landing, and the paths are raised concrete tracks through jungle, gardens and past stilt houses. There is a park with a lake, a weekend floating market, and almost no traffic.
Go early. The tree cover helps but the heat still builds.
The parks at dawn and dusk
Lumphini — the central park, with monitor lizards up to two metres long, a lake with pedal boats, and mass aerobics sessions at either end of the day that anyone can join.
Benjakitti, adjacent, extended in recent years with wetlands and elevated walkways.
Rot Fai Park, further north, large and used for cycling.
All busiest and most pleasant before eight and after five.
The river and the canals
The Chao Phraya express boat works at any hour — moving air, shade under the roof, and the best sightseeing in the city for 16–33 baht.
The Thonburi canals, across the river, retain a network of khlongs with stilt houses, temples and a floating community. Long-tail boat trips run from several piers.
It is a different Bangkok, and it shows how the whole city once functioned before the canals were filled in for roads.
Early morning
The best hours, and almost nobody uses them.
Temples at opening — the Grand Palace at 8am is a different place from the Grand Palace at 11.
Markets — the flower market at Pak Khlong Talat is busiest overnight and early.
Alms giving, when monks walk the streets at dawn.
Day trips outdoors
Ayutthaya, 90 minutes — the former capital's temple ruins, best cycled between in the early morning.
Khao Yai National Park, three hours — Thailand's oldest, with waterfalls, hiking and wildlife including wild elephants.
Kanchanaburi, three hours — the river, Erawan Falls' seven tiers, and the war history.
Evening outdoors
Rooftop bars, once the sun is down.
Chinatown's street food, which sets up along Yaowarat after dark.
Night markets — Rot Fai and the others, which exist precisely because the daytime is unusable.
Practical
Water constantly. Dehydration is the actual risk rather than sunburn.
The BTS, MRT and malls are air conditioned and are the practical refuge for the middle of the day.
November to February is the cool season, which in Bangkok means around 30°C rather than 35 — still hot, and considerably more workable.
The rainy season, roughly May to October, brings short heavy afternoon storms rather than all-day rain.