The K79 Room Hostel is a good clean and cheap hostel in Bangkok. It is for low budget backpackers and is one of the better backpacking hostels in Thailand. The price range is from 400฿ (US$14) to 800฿ and this is really low. The hostel is well known, centrally located and clean.
If you are looking for another budget stay in Thailand you might also look at the listing of the Nantra Ekamai Hotel which is in the 700฿ range but has more amenities than this hostel. Both are located near the BTS Skytrain system so getting around is very easy. The K79 Room Hostel is located near the BTS Phra Khanong Station. There are only two reviews on the Agoda system and both are very positive as they had been solo travelers to Thailand. The hostel is considered clean, nothing better for a budget traveler and best of all there are loads of budget stores around including a Tesco store. All within walking distance.
The hostel is considered a 2 star hotel in its ratings and provides room service, laundry services and also WiFi in the open public spaces. Note that this hostel considers children over 7 to be adults and will be charged accordingly. If you are a backpacker to Thailand then consider the two options and also ensure that you have a Thai tourist visa before you arrive as immigration rules do change in Thailand.