Diarrhea in Children in Koh Samui: What to Give Them and When to Get Help

Clinically reviewed by Dr. Ponlawat Pitsuwan, Physician, Doctor Samui. Last reviewed: October 2026

Your five-year-old was fine at breakfast, running along Chaweng Beach by ten, and by afternoon he is on the bathroom floor. It happens fast here. Parents call it Samui belly, and it is one of the most common reasons families need help mid-trip.

The good news is that most cases are manageable. The problem is that a lot of parents reach for the wrong thing first. What your child actually needs depends on their age, how long this has been going on, and what else is happening alongside the diarrhea.

What Is Causing Your Child’s Diarrhea on Koh Samui

Most child diarrhea here falls into three categories: viral, bacterial, or a reaction to a big change in diet and environment.

Rotavirus hits young children hard, especially in villa and resort groups where it spreads between kids sharing pools or play areas. Norovirus circulates on snorkeling boats, ferries to Angthong, and shared resort buffets. These viral infections do not respond to antibiotics and usually pass within two to three days.

Bacterial causes are more serious. Campylobacter is common in Thailand, often picked up from undercooked seafood at beachside restaurants. Salmonella is linked to resort buffets left out in the heat. Both tend to cause more intense symptoms and often need treatment.

Parasites like Giardia cause diarrhea that drags on for weeks rather than days. If your child’s symptoms are not improving after five to seven days, a stool test matters.

How to Spot Dehydration by Age

Koh Samui’s heat and humidity mean children dehydrate faster here than they would at home. A toddler losing fluid through diarrhea in thirty-three degree heat needs replacing much faster than the same child on a cool day in Europe.

Babies under 12 months

Count wet nappies. Fewer than four in twenty-four hours is a warning sign. Look for a sunken soft spot on the top of the head, no tears when your baby cries, and unusual sleepiness or limpness. These signs in an infant mean get help now, not tomorrow.

Toddlers aged one to three

Look at the mouth: is it dry? Are the eyes sunken? Is your toddler not wanting to move or make eye contact the way they usually do? Dark urine, or no urine in several hours, tells you the same thing. A listless toddler in this heat needs oral rehydration salts immediately, and a doctor if they cannot keep fluid down.

Older children aged four and above

Ask them directly. Older children can tell you they feel dizzy or have not needed the toilet for hours. Dark yellow urine, dry lips, and a headache alongside diarrhea are all signs to act on. Dehydration at this age can also cause confusion, which parents sometimes mistake for tiredness.

What to Give Your Child: Hydration by Age

The only thing that truly matters in the first hours is fluid. Specifically, oral rehydration salts. These replace the salts and sugars that diarrhea strips out. Plain water alone does not do this.

ORS sachets are available at every 7-Eleven on the island and at pharmacies along Chaweng Beach Road. Mix one sachet with the stated amount of clean water. For babies under six months, a doctor should guide dosing. For children six months to two years, aim for fifty to one hundred millilitres after each loose stool. For older children, push as much as they will take.

Breastfed babies should continue breastfeeding throughout, offered more often than usual. Formula-fed babies can continue their normal formula, though a temporary switch to a lactose-free option can help settle the gut. A doctor at our Chaweng clinic or during a villa visit can advise on this.

Coconut water can work as a short-term stopgap if you cannot get ORS immediately, but it does not contain the right balance of sodium. Get proper ORS as soon as you can. Sports drinks, fruit juice, and fizzy drinks are not appropriate for children with diarrhea. The sugar content is too high and can make things worse.

What Not to Give Your Child

This is where parents most often go wrong, and where the pharmacy shelf here can genuinely mislead you.

Loperamide, sold as Imodium, sits on the shelf at every pharmacy on the island. Do not give it to children under twelve. It slows the gut but does not treat the infection. In a child with a fever or blood in the stool, it can trap bacteria inside and make things significantly worse. If you are standing in a pharmacy reading this, put it back.

Adult anti-diarrhea preparations and antispasmodic tablets are not appropriate for children. Ask a pharmacist for oral rehydration salts and nothing else, unless a doctor has already assessed your child and given different guidance.

Probiotics are unlikely to cause harm and may help slightly, but they are not a substitute for rehydration.

Feeding Your Child During and After Diarrhea

The old advice was to stop eating and rest the gut. We do not follow that now.

Keep feeding your child. Offer small amounts of plain, easy food. Khao tom, Thai rice soup, is available from almost any local restaurant on Koh Samui and is gentle on an unsettled stomach. Plain rice, banana, and crackers all work. Avoid fatty or heavily spiced food until the diarrhea has settled for at least twenty-four hours. For babies and toddlers, continue milk feeds. Withholding food slows recovery, not helps it.

When Antibiotics Are Needed for Child Diarrhea on Koh Samui

Most child diarrhea on Koh Samui does not need antibiotics. Viral gastroenteritis will not respond to them. But Campylobacter, Salmonella, and Shigella sometimes do.

Here is something that matters specifically in Thailand. Campylobacter in this region is largely resistant to ciprofloxacin, the antibiotic pharmacies often suggest for traveler’s diarrhea. It will not clear the infection in many cases. Azithromycin is the preferred choice for children with suspected bacterial diarrhea in Thailand, but it needs a proper assessment first, and ideally a stool test.

This is why buying whatever the pharmacy recommends is not always safe. The right antibiotic for your child here is different from what might work in Europe or North America. At Doctor Samui, we can run a stool test and prescribe based on what your child actually has, not a guess. Our family health services include paediatric assessment and stool culture.

When You Should Not Wait

Some situations need a doctor, not a pharmacy run.

Get help if your child is under two and has had diarrhea for more than twelve hours. Get help if there is blood in the stool at any age. Get help if your child has a fever above 38.5°C alongside diarrhea, or is vomiting so often they cannot keep any fluid down for more than two hours.

If you are staying in Maenam, on the north coast, or anywhere that feels far from Chaweng at midnight, do not put your child in a car if you are not sure it is the right call. Doctor Samui runs 24/7 hotel and villa visits across the whole island, covering Maenam, Bophut, Lamai, Choeng Mon, and Nathon. A doctor can come to you, assess your child, take a stool sample on-site, and give IV rehydration at your villa if needed. For a sick toddler refusing fluids at two in the morning, that is often the right call.