Mold grows wherever damp air meets a surface that stays wet or cool, and in Thailand that can be the back of a wardrobe, a leather bag or the inside of a camera lens within weeks. The fix is mostly about moving and drying the air: run the air conditioner or a dehumidifier, keep air circulating behind furniture, and deal with any leak at once.
Visitors on a two-week holiday rarely notice. Residents do, especially after their first rainy season, or after leaving a condo closed up for a month while they travel. Thailand's air is humid for much of the year, and closed rooms with no air movement are where mold starts. This page covers prevention, cleaning small patches safely and what to do in a rented home. (We use the American spelling "mold" in the text; British readers will know it as mould.)
Keeping a Thai home dry
- Indoor humidity to aim for
- Below 60%, ideally 30 to 50% (US EPA); at or below 50% (US CDC)
- After a leak or spill
- Dry wet items and surfaces within 24 to 48 hours
- Main tools
- Air conditioner (dry mode), dehumidifier, fans, ventilation
- Small patch on a hard surface
- Scrub with water and detergent, then dry completely
- Large area or after flooding
- Get professional help; tell your landlord
- Cleaning products
- Never mix them (US EPA and CDC)
Why mold matters for your health
The World Health Organization's guidelines on dampness and mold say the most important health effects of damp buildings are more respiratory symptoms, allergies and asthma, and disturbance of the immune system. Its main advice is simple: prevent persistent dampness and microbial growth on surfaces and inside the building structure. The US Centers for Disease Control and Prevention (CDC) adds that people with asthma or mold allergies can react severely, and that people with a weakened immune system or chronic lung disease can develop lung infections. If you notice breathing problems that improve when you are away from home, mention it to a doctor. Our page on hospitals in Thailand explains where to go.
Killing mold is not enough. The US Environmental Protection Agency points out that dead mold can still cause allergic reactions, so it has to be removed, and the moisture that fed it has to stop, or it comes back.
Where mold starts in a Thai home
Knowing the usual spots lets you check them every few weeks:
- Wardrobes against an outside wall, especially built-in ones with no gap at the back.
- Behind and under furniture pushed tight against walls: sofas, beds, bookcases.
- Bathrooms without a window or working extractor fan, in grout and silicone around the shower.
- Around the air conditioner: the indoor unit, its drain line, and the wall or ceiling below it if the drain leaks. Our guide to air-conditioner cleaning covers servicing the unit itself.
- Window frames and ceilings where rain gets in, or where a neighbor's leak comes through from above.
- Shoes, bags and belts in leather, and anything stored in a closed plastic box while still slightly damp.
A musty smell is often the first sign, before you see anything. Follow it.
Air conditioner dry mode, fans and ventilation
An air conditioner removes moisture from the air as it cools, which is why water drips from its drain pipe. Most units also have a dry mode, usually marked with a water-drop symbol, which runs the unit to reduce humidity with less cooling. Running dry mode for a few hours a day in a closed bedroom or wardrobe room makes a clear difference in the wet months. Keep the filters clean, because a dirty unit dries the air less well and can itself become a place where mold grows.
Air movement matters as much as dryness. A fan pushing air along a wall, or a gap of a few centimeters between furniture and walls, stops the still, damp pockets mold likes. Open windows on dry, breezy days. Close them during heavy rain and on muggy evenings, when the outside air is wetter than the inside.
Leaving your condo closed for weeks invites mold. Before a long trip, empty the fridge and leave its door ajar, prop open wardrobe and cupboard doors, and ask the building or a friend to air the unit or run the air conditioner on dry mode once or twice a week. A dehumidifier with its drain hose led into a sink or shower drain can keep running while you are away.
Dehumidifiers and moisture absorbers
A plug-in dehumidifier pulls water out of the air into a tank or through a hose. It suits a room you cannot ventilate, a storage room, or a home that stays closed while you travel. When choosing one, look at how much water it removes per day, how large its tank is, whether it can drain continuously through a hose, and how loud it is in a bedroom. It runs on electricity like the air conditioner; our cost of living guide shows what a unit of power costs. A small hygrometer, a cheap humidity meter, tells you whether it is working: the EPA suggests keeping indoor humidity below 60%, and the CDC at or below 50%.
Disposable moisture absorbers, the small boxes or hanging bags sold in Thai supermarkets, collect water in a reservoir. They help in a wardrobe or a shoe cupboard, but they cannot dry a whole room. Replace them when full, and keep them away from children and pets. Silica gel sachets do the same job in a camera bag or a box of documents.
Clothes, leather, cameras and documents
Clothes. Never put clothes away damp, including from a dryer that did not finish the job. Leave space between hangers, and wear or air everything in the wardrobe now and then. If you use a laundry service, check that items come back fully dry before you put them away; our page on laundry in Thailand explains the options.
Leather. Shoes, belts, bags and jackets are among the first things to grow mold. Store them in cloth bags rather than plastic, in a room that is dried regularly, and wipe them down every few weeks.
Cameras and lenses. Fungus can grow inside lenses and is often impossible to clean without a repair shop. Keep camera gear in a sealed box or bag with silica gel, or in a dry cabinet, and use it regularly; light and air movement discourage growth.
Documents. Passports, title deeds, certificates and photos stored in a damp drawer can stain and stick together. Use sealed plastic folders with a silica gel sachet, and keep scans of everything important.
Cleaning a small patch safely
For a small area on a hard surface such as tiles, a painted wall or plastic, the EPA advises scrubbing with water and detergent and then drying the surface completely. Wear gloves and eye protection, and a properly fitted N95 mask if you are sensitive, and keep the room ventilated while you work.
Porous materials are harder. Mold in a mattress, carpet, ceiling board or fabric sofa may be difficult or impossible to remove completely, and the item may have to go. If the mold covers a large area (the EPA's threshold is about 10 square feet, roughly one square meter), if it follows heavy water damage, or if dirty floodwater was involved, get professional help instead of cleaning it yourself.
Do not mix cleaning products. The EPA and the CDC both warn that mixing chlorine bleach with ammonia or other cleaners releases poisonous gas. Use one product at a time and read the label.
Clean the surface, then fix the cause. If the wall is damp because of a leak in the pipe behind it, the mold will be back within weeks, however well you scrub.
Rented homes: telling the landlord and your deposit
If you rent, mold is often a building problem: a leaking pipe, a faulty air-conditioner drain, rain coming in through a window seal, or water from the unit upstairs. Report it in writing, with dated photos, as soon as you find it, and ask the landlord or the condo office to find the source. That record matters when you move out, because a deposit dispute often comes down to whether damage was reported or ignored. Our guide to renting a condo or house explains the move-in inventory, the 2025 rules on deposits, and getting the deposit back; take photos of walls, wardrobes and ceilings at move-in so you can show what was there before you.
Your own habits count too. Drying clothes indoors with the windows shut, never running the air conditioner or a fan, or leaving the unit closed for months can let mold grow in a sound building. Who pays for the repair depends on the cause and on your lease, so read the repair clause and agree in writing before work starts.
The rainy season and after a flood
Humidity peaks in the rainy season; our page on the rainy season in Thailand describes the weather month by month. That is the time to check wardrobes and leather more often, run dry mode daily and keep an eye on ceilings after storms.
Flooding is a different scale of problem. After water has entered a home, everything wet must be dried within a day or two, or removed, and electrical items need an electrician's check before use. Our guide to flooding at home covers preparation, and floodwater carries its own infection risks, explained in our page on leptospirosis and melioidosis.
Frequently asked questions
What humidity should I keep my Thai condo at to stop mold?
The US Environmental Protection Agency recommends keeping indoor humidity below 60%, ideally between 30 and 50%, and the CDC says at or below 50%. A small hygrometer shows the reading, and an air conditioner on dry mode or a dehumidifier brings it down.
Does air conditioner dry mode really help with mold?
Yes, it removes moisture from the air while cooling less than normal mode. Used regularly in closed rooms during the wet months, it helps keep wardrobes, leather and walls dry. Keep the filters and drain clean so the unit itself does not grow mold.
How do I stop mold in my wardrobe in Thailand?
Leave a gap between the wardrobe and the wall, open the doors regularly, never put clothes away damp, and use moisture absorbers or a dehumidifier in the room. Store leather in cloth bags rather than plastic, and check the back wall every few weeks.
Can I clean mold with bleach?
For small patches on hard surfaces, the EPA's basic advice is water and detergent, then thorough drying. Whatever product you use, never mix it with another cleaner: the EPA and CDC warn that bleach mixed with ammonia or other cleaners gives off poisonous gas. Large areas need professional help.
Who pays for mold damage in a rented condo?
It depends on the cause and on your lease, and we cannot give a general rule. A leak from a pipe, the building or the unit above is a different case from mold caused by how a unit was used. Report it in writing with photos as soon as you see it, and read the lease's repair clause.
Sources
- World Health Organization – Guidelines for indoor air quality: dampness and mould (2009) (checked October 2026)
- US Environmental Protection Agency – A Brief Guide to Mold, Moisture and Your Home (checked October 2026)
- US Centers for Disease Control and Prevention – About mold and your health (checked October 2026)