we stayed at suk 11 backpackers' hostel
http://www.hostelz.com/hostel/31082-Suk-11-Hostel in bkk september of last year. we had a decent accommodation
there were four of us so we had a private suite with bathroom. easy on the budget too since we only shelled out 400+ [in pesos] per night. they serve a daily breakfast of coffee, croissants and fruits till 10am and you get to meet a whole lot of interesting travelers, mostly caucasians
the place is a bit rickety, since it's literally a house and at first glance, it looks awfully small, but when you get inside you'll see nga mura diay ug MAZE...there are corridors leading to rooms and mini stairways leading to other rooms pa jud! it's near the nana station, so it's very convenient & accessible to the shopping destinations.
i don't know if they accept online reservations though since we had our room reserved through a friend who was actually there during our planning stages. siya ra ang personally arrange sa tanan.
good luck!