I have always been very comfortable at the Majestic Suites (
http://www.majesticsuites.com/main.html ) on Sukhumvit.
It is very clean, excellent staff, and guest-friendly.
The cheaper rooms are a bit on the small side, but the deluxe ones are good.
If you get a top floor room at the back, you can see into Nana Plaza, and it's a ten minute walk to Soi Cowboy.
Cheers
LL