From TripAdvisor: Bangkok Loft Inn Bangkok, Thailand from $28/night "Incredible value for money! in a nice peaceful area" more by
New Joe Guest House: Khao San Road, Bkk. Website: website here.
A single room with fan and bathroom for 300 Baht (under US$12 per night).
Sawasdee Welcome Inn: 5-7 Soi Rongmai, Chao Fa Rd., Phanakorn, Bkk. 10200. Website: website here.
A standard single room for 300 Baht a night in low season, which lasts from April to Novemeber. This rate includes VAT and service charge.
Shadow Inn Bangkok: 550 Vanich 1, Sampathawong.
Dorm beds for as low as US$3.77 a night, according to AsiaRooms.
Shambara Boutique Hostel: Khao San Road, Bkk. Website: website here.
A single with fan can be found for 300 Baht.
The Overstay: . Website: website here.
Part youth hostel, part nightclub, part Warholian artspace. Also one of the cheapest places to stay in Bangkok, only AUD$5 a night for a private room with shared bath. Hosts entertainment events like Viet Cong Babes Versus GI's, and the like. Dorm beds cost 80 Baht a night, while individual rooms go for 150 Baht per night.
Train Inn: Near Bangkok Railway Station. Website: website here.
A new boutique hotel. 3rd class rooms with air-con and cable TV cost 450 Baht per night.
Wild Orchid Villa Khaosan: 8 Soi Chana, Songkhram, Bkk. Website: website here.
A single with fan and shared bathroom for 250 Baht per night.