Dengue is a key Thailand risk because the mosquitoes that spread it often bite during the day and are common in towns and cities as well as resort areas. There is no tablet you can take to prevent dengue. Bite avoidance still matters: repellent, covered skin when practical, and accommodation with screens or air conditioning can all reduce exposure. Zika is also reported in Thailand, so pregnancy or plans to conceive soon should be discussed before travel. Hepatitis A is commonly recommended for previously unvaccinated travellers because it spreads through contaminated food and water. Tetanus should be up to date, especially if you may ride scooters, trek, dive, cycle or spend time away from easy medical care. Typhoid vaccination may be considered for longer stays, repeated travel, lower-budget travel or visits where food hygiene is less predictable. Rabies is present in Thailand. Dogs are the main concern, but any bite, scratch or lick to broken skin needs urgent medical advice. Pre-travel rabies vaccination is worth discussing for children, runners, cyclists, long stays and rural itineraries. Japanese encephalitis occurs in Thailand, with higher relevance for longer stays in rural areas, especially around rice fields or pig farming areas, and during the May to October transmission season in northern regions. Hepatitis B may be relevant for longer stays, sexual exposure, contact sports, medical treatment abroad or work involving blood or body fluids. Malaria is not a major issue for most standard Thailand holidays. Risk is low in rural, forested border areas with Cambodia, Laos and Myanmar, very low elsewhere, and not expected in Bangkok, Chiang Mai, Chiang Rai, Koh Samui, Koh Phangan or Pattaya. Yellow fever vaccination is not a Thailand risk requirement, but a certificate can be needed if you arrive from, or transit for more than 12 hours through, a country with yellow fever risk.