BTS is Bangkok elevated rapid transit system, which is known as Skytrain. With BTS, you can go to the major areas in Bangkok without facing traffic jams. Currently BTS has 2 main lines: Sukhumvit line and Silom line.
Saphan Khwai is a BTS station on Sukhumvit line that is located on Phahon Yothin Road, near Saphan Khwai Intersection in Phaya Thai District.
Here is the map for the area around Saphan Khwai BTS Station. I have got this map from BTS official website. The area map for the other BTS stations can be found here. To enlarge, click at the map.
What to see around BTS Saphan Khwai Station
From the map, you will see that this area has condominiums, banks, and supermarkets. Not so many things to see in the area. No big shopping malls, temples, or historical sites.
Sam Sen Nai Philatelic Museum or Stamp museum is the only museum in this area.
Well, if walk around, you will find out that there are several specialty shops or stalls such as second-hand book shops, amulet stalls, and local restaurants in the area. You can do street shopping here.
Hope this information helps. Enjoy traveling Bangkok!