Before traveling to Thailand, you should at least consider vaccination against the following diseases:
• Hepatitis A and B — caused by an intestine virus attacking the liver and thus causing jaundice. The virus can transmit via blood or unprotected sexual intercourse. Havrix is a combo vaccine that gives protection against hepatitis A as well as B.
• Cholera — a contagious intestine illness transmitted through food and water. Luckily, cholera epidemics are very rare in Thailand.
• Typhoid — a salmonella bacteria also transmitted through food and water. Headache and high fever are characteristic symptoms.
• Rabies — does exist in Thailand but vaccination is normally not recommended unless bitten by an infected animal, most often a dog.
• Japanese Encephalitis — a severe virus disease that can cause highly acute complications by affecting the central nervous system. Again, luckily, it is very rare and vaccination is not needed unless you plan on staying for longer periods in Thailand. Japanese Encephalitis is commonly spread by mosquitoes.
• Malaria — also spread by mosquitoes, causing substantial number of deaths in developing countries. Even though there is malaria in Thailand, cities and holiday resorts have been free from the disease for many years. Bear in mind that mosquitoes are not fond of air conditioning, meaning that using it night-time allows you to kill two birds with one stone!
• Diphtheria, Polio & Tetanus — diseases against which most westerners already have protection. If not, indeed consider replenishment or complete vaccination.