It has several big centers within the city. Depends on your interests, choose your hotel accordingly - the main shopping areas are Silom, Sukhumvit, and of course the Riverside where the top top hotels are located. Hotels in Bangkok are cheap, so it is wellworth to splurge for a 5 or 6 stars. Marriott Resort is a 4 star along the river. There is a JW Marriott (the highest level in Marriott hotel group) at Sukhumvit - the mega shopping centers area.
2) You can avoid road traffice by 2 ways - take the Skytrain (forgot if it is the correct name), or take the boat along the Chao Phraya River. There are public ferries zooming along the river. Most all hotels along the river also provide shuttle boats.
3) You can take public buses which are dirt cheap but there is a language barrier of course.
There is also a China Town in Bangkok - you can explore it for sightseeing purposes, but dont expect a whole lot - it is probably the dirtiest, noisiest and crowdiest China Town you would ever encounter.
4) There is a HUGE night market in Bangkok - if you are adventurous, it is well worth the effort to go. I guess books like Lonely Planet etc would have detailed deion. I dont remember if it is Chatuchak. Be prepared for extreme heat. Pratunam, Pahurat and Chatuchak all are open-air, extremely crowded markets.
A new night market is opened recently called Suan Lum, which is reportedly is under covered walkways so it is less hot.
5) Dept Stores in Bangkok are very highclass sell all sorts of top class brand names but are much cheaper than in Hong Kong. If you are into shopping, you will find yourself in heaven.