actually there is not only the mentioned "dodgy" entertainment available in this area. in particular Soi 11 is a party street with many bars of the non-dodgy kind (it was dodgy-free for long time but now some dodgy bars are spreading there as well)....
I have stayed in Mercure in Soi 11. It is a decent hotel and not too old; I got an upgrade to the executive room and lounge access as I am Platinum. Landmark hotel is getting old, but is great from the location (for those who want to stay there). Movenpick in Soi 15 is a bit far for walking back to Sukhumvit but also a good middle class hotel