I stayed at Sri Hualamphong Hotel for a couple of nights two years ago, and I definitely would recommend it to any independent, non-fussy traveler on a budget. I paid about 250 baht ($5 at the time) for my own room (with bathroom); it wasn't luxurious or well-lit, but it was clean, and that was what mattered to me. It's true, there's no hot water or concierge, but you have to be willing to spend quite a bit more if that's what you're looking for. The location is also fabulous, right next to the train station and around the corner from a subway station, to take you anywhere in Bangkok, and not too far away from the water taxi either. Also, as a woman traveling alone I felt safe at this hotel, which is a major point in its favor.