Thailand has been known as a shopper's paradise for many years. From luxurious items such as jewelry, silk, designers' clothing or accessories right down to the best of bargained goods. Fixed prices are the norm in shopping centers or department stores but at most other places like markets, street-stalls, etc., haggling is acceptable and expected. There're no fixed rules when it comes to bargaining, generally you can get somewhere between 10-40% from the asking price. Depending on your skills and sometimes the shopkeeper's mood. Being courteous with a sense of humor goes a long way when bargaining in Thailand, as Thais appreciate good manners. Being angry when bargaining will get you nowhere.
Another great thing about Thailand shopping is, even in Bangkok alone, the shopping is not limited to one or two shopping streets. There're many areas throughout the city offering various choices and easy access. For example, Silom, Sukhumvit, Siam Square, Chatuchak weekend market or China Town. Many other cities outside of Bangkok also offer great shopping. Chiang Mai is ideal for traditional Thai handicrafts while Phuket is a great source for pearls and Pattaya has a wide selection of precious stones since it's close to Chantaburi where numerous gems are found.