evidence: But don't worry about animals. Ko Samui is very well developed unless you go out in the middle of the islan your chance of seeing anything dangerous is remote. You will see geckos, ants, spiders, and such. After 12 yrs traveling to Thailand and 4 yrs living up north in the countryside the only thing I have been bitten by are Mosquitos. Although I would stay clear of Thai dogs. Most do not like the smell of toursits. No joke on that one. Best to avoid them if possible. [...] I am serious in saying that the most dangerous animal you are likely to encounter is a pack of feral dogs. They are often disease ridden and should be avoided. The gecko mentioned by packhike is your friend. It lives in hotelrooms, houses etc and eats nasties like mosquitos and spiders. Snakes are common but rarely seen by visitors as they are usually sensible enough to stay away from humans. Giant man-eating kittens often leap out of hotel closets!