There are 3 types of shopping areas in Thailand.
Classic USA style. Big, beautiful, modern enormous, multi level, shopping mails, with popular, designer names with all of the cool fashions, cosmetics, etc from around the world. They even full restaurants, food courts, public parking, live entertainment and usually some type of event in order to attract the tourists.
Lower end shopping plazas. There are usually crowded, discounted malls, with loads of cheaper merchandise, lots of knock offs, lower end restaurants and of course food courts. These are very popular with the locals and those who like to haggle over price.
Street Vendors and Street fairs. Unlike the USA, Thai businesses (very small business) are allowed to setup shop on the sidewalk in front of an existing structure. While this leads to difficulty in walking, it provides for an abundance of tourist merchandise available for a very inexpensive price. Here you can bargain away over price all day long.
Shopping Malls in Bangkok
Asiatique The Riverfront
Central World Plaza
Note: ALL of the above are located near a BTS Station
Shopping Malls in Phuket
Central Festival, Phuket Town
Jungceylon, Patpong Beach