At one time, back in the 1970s, Asoke Road, which is also properly known as Sukhumvit Soi 21, was the eastern edge of Bangkok. The name of the street seems have Japanese origins, but I'm not sure. Until recently, the Japanese embassy was near the Petchburi end of the road. The map below includes most of the Nana area, which abuts Asoke to the west.
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Base map image © OpenStreetMap contributors, CC BY-SA
The Asoke area, and in particular the Asoke intersection, where Asoke and Sukhumvit cross, is perhaps most well known for it's bad traffic. Traffic in the area is still heavy, but thanks to the trains and new expressways, it's not nearly as bad as it was 20 years ago.
Nana is also a famous area of Bangkok, but for completely different reasons. The Nana Entertainment Complex, on Nana Road, is infamous as one of Bangkok's seedier areas for bar girls, go-go bars and the like.
Owing to the rather central location and all the transportation options, there are quite a few hotels in the Asoke area, in all prices. It might not be my first choice for locations to stay, especially for a first visit to Bangkok, but if you're a frequent visitor or just have a one or two night layover to spend in the city, it would be a handy area to choose.