Up top is Asoke Skytrain Station (BTS) down below is Sukhumvit Subway Station (MRT). The Asoke Interchange Station is the only place where the skytrain and subway meet in the Sukhumvit area. Follow the signs at stations to connect between the two (Exit 3 on each).
The nine story Terminal 21 Shopping Mall sits next door to the Asoke Interchange Station and is connected by an elevated skywalk. In the adjoining tower is the 5* Grande Centre Point Sukhumvit Hotel (surprisingly affordable).
Further on the elevated skywalk connection bridge you will find the Interchange Building, Exchange Tower, Robinson and the Sheraton Grande Hotel.
Interchange Stations in Other Areas: Silom area is the Saladeng (BTS) and Silom (MRT) interchange. In the further Chatuchak area is the Chatuchak (MRT) and Mo Chit (BTS) interchange.