http://bangpli.com/sananwan.htm is a guesthouse near the airport that several here have recommended.

Also, on Asiarooms.com some of the places I looked at that had good reviews were:
Bangkok Boutique--has wireless internet
Royal Benja--hasgym,
Bossotel --says internet broadband all rooms. Exercise room. Walking distance to river
TheBedrooms -- Has wi-fi