The following are very low cost hotels under 1,000 baht/night. All but one are in the Suk area. They aren't hotels where I would stay more than one night, but that is what some punters need or want - a very cheap place for a short stay.
Here's a very basic, but clean, no-roach hotel with A/C at 700B/night, close to Nana:
Thai House Inn
An even cheaper place is
NumberOne Guest House Trivia Question: Why does this place occupy a special place in the history of Bangkok P4P? It will be fun to see if any "veterans" get the answer right.
Not the best location, but very low price:
Honey Hotel
Way outside the Suk area, but great value for money under 650B/night. Taxi/moto will get you to the lower Suk. The colorfully named
NasaVegasHotel
I've never stayed at this place, but I got a tip that is very good value for money at under 1,000B/night for a room. Here's the link:
NAP-Inn
Evil