If not, then chat to your local doctor. Many western hospitals will advise taking precautionary medical measures against the possibility of contracting the disease but those that live in malaria infested areas, around the world, not just in Thailand, advise against this. The reason for this is that if you are on medication and still contract malaria, it is harder to detect than if you are on no medication at all. Some travelers prefer to carry the cure with them rather than taking preventative measures all the time. The choice therefore is yours entirely but do speak to your local doctor before visiting.
Dengue fever is another mosquito born illness that is prevalent in most parts of south-east Asia.
Complications with the disease, which can lead to death, usually only occur on a second infection and although causing severe headaches and body pains and general weakness, there is no preventative medicine. The only way to avoid contracting the disease is to protect yourself against mosquito bites as best possible. Hospital care is possibly not exactly what you might be used to unless you happen to be in one of the main centres. It is generally a good idea to take out some form of travel insurance that includes medical cover and if suffering from some complaint, bring a supply of any medication you may require during your stay. Medicines can be bought directly over the counter, though your particular brand may not be available.