There is absolutely no denying that there is a significant difference between the general impression most tourists have of Thailand and the reality that expatriates and, indeed, the Thais themselves live with. Start to ask yourself: What is Thai for you? Thai food, Thai jasmine rice, Thai massage, Thai boxing, Thai silk? These are all well known around the world and are certainly worthy of photographing, but several of these are not part of your average Thai’s everyday life.
Take a walk down a Bangkok street or a ride on the BTS and look around you at Thai culture in action. Many temples are open to tourists — just be sure to dress appropriately (closed-toed shoes, shorts/pants that cover the knee, no bare shoulders) and act respectfully (no hats, sunglasses, smoking, gum chewing, or overly loud talking, and remember to remove your shoes before entering worship areas and to wield your camera thoughtfully).
Buddhist monks are fascinating figures in photography for example. My experience is that they are often happy to be photographed, especially if you take the time to chat a little with them. Many monks are young and ambitious men eager to practice English. Just give it a try!