We've been there several times, both to Bangkok and to various hotels around the country. Are you going to Bangkok or one of the resorts? And what kind of info do you want?
The "wet season" is over, and just about now is the peak tourist season. Like Hisgirl mentioned, it'll be hot and humid. Not so sure about the "conservative dress" part, however, unless you are thinking of visiting one of the many beautiful temples. On the beach, just about everything goes (with the exception of topless). And in Bangkok, you'll see farang (Westerners) dressed in all kinds of clothing; the more relaxed the better. I've been to several business meetings in Bangkok, and it's rather unpleasant to feel, after walking only a block or two, that you need to change your shirt / blouse.
The food is great. Thai food is one of the world's great cuisines, and much (not all of it) is spicy. Cooked street food is relatively safe to eat, especially if there are lots of Thai customers (there usually are!), which means that the food has not been sitting around long.
Bangkok is also great for shopping. The Silom area has a mind-boggling number of glitzy department stores and shopping centers, and for example the Chinese and Indian sections of the city are great for the markets. The Bangkok Night Market is huge, and you can get just about anything you want (and a lot of things you wouldn't ever want). Thai silk is beautiful; Jim Thompson revived the Thai silk industry back after the Second World War, and the Jim Thompson stores have lots of lovely gifts.