When it rains: the indoor Bangkok repertoire.

Understanding the rain before you plan around it

The Bangkok wet season runs from roughly May to October, with September and October usually the heaviest. What it does not mean is days of continuous grey. The typical pattern is a bright, hot morning, a build-up through the early afternoon, and a violent downpour somewhere between two and five that lasts an hour or two and then stops, leaving the evening washed and pleasant. That pattern is the whole planning insight. Mornings in the wet season are usually usable and often lovely. The afternoons are the problem, and the afternoons are precisely when a family with young children most needs somewhere to be.

The second thing to understand is that the rain does not simply make you wet, it makes the city stop. Surface streets in parts of Bangkok flood quickly, traffic seizes, and a journey that takes twenty minutes at noon can take an hour at four. That is why the indoor plan should be indoors and close, ideally reachable on the BTS Skytrain or attached to the hotel, rather than a brilliant idea forty minutes away. The families who cope best treat the wet season afternoon as a fixed feature of the day and book something for it in advance, exactly as they would book a restaurant.

The aquarium and the science of a wet afternoon

The default and the reason it is the default: Sea Life Bangkok Ocean World, in the basement of Siam Paragon at Siam BTS station, is a large, well-run aquarium with a tunnel, a glass-bottom boat and feeding sessions, and it absorbs two hours of a small child's afternoon reliably. It sits under a mall, which means the whole outing from car to lunch to aquarium to shopping happens without stepping outside, and the mall is directly connected to the Skytrain. For children roughly three to eleven it is the single most useful wet-afternoon booking in the city.

In the same building, KidZania is the other long-standing option: a scaled indoor city where children take on jobs, earn a currency and run around unsupervised in a controlled environment. It works best for six to twelve year olds and it is genuinely tiring in the way parents want. Both should be booked online in advance during Indian school holidays, when the queues are long and the tickets at the door are the expensive ones. Further out, the Bangkok Planetarium at Ekkamai is an old-fashioned and inexpensive science centre that has entertained several generations of Bangkok children and is a pleasant alternative when the malls feel overwhelming.

Museums that work with children

Museum Siam, near the old city, is the one we send families to first, because it was designed as an interactive museum about Thai identity rather than a cabinet of objects, and children move through it rather than filing past it. The Bangkok National Museum is the serious one, with the finest collection in the country, and is better suited to teenagers and adults than to small children; go in the morning if you go. The Jim Thompson House, the teak compound of the American who revived the Thai silk industry, is a guided walk through a beautiful house and garden that takes an hour, is largely under cover, and is close to Siam, which makes it a good pairing with a mall lunch.

For older children and teenagers there is a further layer: the contemporary art centre at the Pathumwan intersection opposite the malls, which is free, calm and covered; the various private galleries in the Chinatown and riverside districts; and the temples of the old city, which are outdoor but where the ordination halls and covered galleries give real shelter. On a rainy day the Grand Palace and Wat Pho are unpleasant, since much of both is open ground and the crowds compress under the eaves, so we move them to another morning rather than attempting them wet.

Malls, which are the city's actual wet weather infrastructure

Bangkok's malls are not a fallback, they are a genuine urban form, air conditioned, connected to the trains and to each other, and each one has a children's floor with play areas, arcades, cinemas and food. The Siam cluster, Paragon, Center and Discovery, is the biggest and holds the aquarium and KidZania. EmQuartier and Emporium at Phrom Phong are the polished option with a good play floor and a large multiplex. Terminal 21 at Asok is the one children enjoy for its themed floors. ICONSIAM on the Thonburi bank of the river is the most impressive of all, with an indoor floating market on its lower floor that serves as a covered street-food hall, and it is reached by a free shuttle boat from the Saphan Taksin pier, which is itself an outing on a wet day.

Inside the malls the useful things are often not the shops. Cinemas showing English-language films with the usual Thai courtesy of a royal anthem before the feature. Bowling and arcade floors. Trampoline and soft-play centres for the under-eights. Ice rinks in two of the larger malls, which children from Mumbai find delightful and slightly absurd. And the food halls, which are the best cheap eating in the city and hold vegetarian options that a briefed adult can navigate confidently.

Things to do that are not sightseeing

• A Thai cooking class in a covered kitchen, with a vegetarian menu arranged in advance; teenagers in particular take to this.
• A hotel spa afternoon, with the family booked into adjoining rooms and the children given a short foot massage rather than a full treatment.
• Muay Thai training at an indoor gym, which turns a wasted afternoon into the best two hours of a teenager's week.
• The hotel pool if it is covered or the rain is warm and there is no lightning, which children enjoy more than anything on this list.
• An indoor market run: the covered lanes of Phahurat for fabric and puja materials, or the Yaowarat gold row, both largely sheltered.
• A film at the mall multiplex, booked online, with reserved seats so the family is not queuing.

The plan itself

The discipline is to hold two of these in reserve at all times during the wet months, booked or at least identified, close to the hotel, and matched to the ages in the group. The office puts them on the daily page alongside the real itinerary so that when the sky goes dark at two the family does not have a conversation, it simply has a car. A wet afternoon that has been planned for is not a lost day. It is frequently the day the children remember.

Opening hours, ticket prices and attraction operators change, and several venues require advance online booking during peak holiday periods. Confirm current hours and availability with each venue directly, and check Tourism Authority of Thailand guidance and local flood warnings during the heaviest weeks of the wet season.

This briefing is general information, not legal, tax or investment advice. Thai rules change frequently and individual cases differ. Verify current requirements with the relevant authorities, including the Immigration Bureau, the Board of Investment, the Land Department, the Department of Business Development and the Revenue Department, and take advice on your own facts before acting.