After coming back from Chatuchak weekend market, I decided to visit King Power Duty Free Shop, which located near Victory Monument. You need passport and return air ticket to enter this building. It sells all range of branded items such as watches, clothes, cosmetics, snacks etc. Usually the cosmetic section is the most crowded place and yes, they are quite cheap.
It is not cash and carry shop. After you paid, they seals your purchased items and sends it to the air port. On the day of your departure, collect your things at the King Power shop at the air port.
Inside the King Power building, there is a traditional show (not free) of this ogre in the theater and an international buffet restaurant.
As first, I planned to take taxi or tuk tuk from King Power to the hotel. But I can see the Baiyoke Tower from here, looks quite close. So I just walk to the hotel, save money for dinner. :)