The Skytrain connects areas popular with tourists! I don't think you will like being in areas that are less touristy because that also means you have fewer places you can easily walk to. In some neighborhoods it gets pretty dull after 9 or 10 pm.
Maybe in the PHAYA THAI area of Pratunam you can avoid some tourists and also avoid nightlife. Hotels like the Florida are close to both the Airport Rail Link and the Skytrain.
If you like shopping then the Pratunam area will do nicely. Nothing says you can not use the Skytrain to take you to some intermediate stops that are not Chatuchak, Sukhumvit, Silom and KSR areas and personally see if those areas will do for you. If you hit the rack early and have little interest in walking to many things then check out some out of the way hotels near less popular Skytrain stops.
http://bangkok.sawadee.com/skytrain.htm
Try asking your question on this forum for more responses:
http://www.tripadvisor.com/ShowForum-g293916-i3687-Bangkok.html