Thailand is a very safe country. Thai food is loaded with antioxidants, and there are a huge variety of fresh fruits and vegetables to stock up on all the necessary vitamins and minerals. Street food is almost always safe, but drinking tap water should be avoided. Few countries offer such a plethora of healthy food options for such a low price.
Thailand also has an excellent medical system that is quite cheap given the high quality standard. Thailand is developing as a medical tourism destination, especially for Americans who seek to escape the ridiculous cost of medicine in their country. Many expats and travelers who are injured or who get sick in countries like Burma, Laos, the Philippines or Cambodia are treated in Thailand, as costs are lower and the doctors and medical facilities are far superior.
Public transport is safer than other less developed countries in the region, though accidents happen. In general, people follow traffic laws and drive reasonably carefully. In the countryside, drunk drivers on motorbikes are common, but no more than anywhere… Some truck drivers and bus drivers take amphetamines to stay awake for days, but again, this is common just about everywhere, and Thailand’s not much worse on this count than the United States, for example.
Violent crime is rare, but robbery is relatively common, especially in tourist areas. Travelers should be aware of pickpockets in bars and crowded markets, and should definitely keep any valuables secured to the body. More elaborate schemes are also common, like identity theft or gem schemes. If a deal sounds too good to be true, that’s because it is. Another risk for travelers (especially those who purchase prostitutes) is date rape drugs. Pattaya is infamous for this. The traveler’s drink is drugged and then they are taken to their hotel where they pass out. They wake up robbed to the skin.
Drunken teenage tourists on break from “Uni” are arguably the greatest threat for the traveler in Thailand. If confronted by one it’s always better to walk away; hopefully in a few years they’ll realize that they were assholes.