Most of Ko Samet, including all the good parts, is part of Khao Laem Ya-Mu Ko Samet National Park and thus has an entry fee. Thais pay 40 baht for adults, 20 baht for children (current as of June 2009); foreigners pay 200 baht for adults, 100 baht for children (current as of November 2009). This two-tier pricing policy is applicable to all national parks. If you can explain, however, that you actually live or work in Thailand, then you may not have to pay the "tourist" price. One excuse for the difference is that "Thai citizens pay taxes". If you are a teacher and work in Thailand you may bring out some form of Thai ID - Driver's LIcense, Teachers card or something like that and you will get the Thai fee.