hi Aissa!
U can also check
www.khaosanby.com
I have stayed on and around Khaosan plenty of times and Buddy lodge right on Khaosarn was nice but a little expensive if u are on a budget. D&D on Khaosarn is ok with single to triple rooms for 550-1000 bath including breakfast buffe and quite nice pool aeria on top floor but noisy as hell if have room facing crazy Khaosarn rd!
Lucky house next to Khaosarn (close to the police station) is good if u are on budget! 350bath for single room and 390 bath for double ,its simple but clean and friendly staff , and u at least have air con,hot water , tv .
If u are on a really tight budget u have some really cheap places around Khaosarn, i cant remeber tha name now but once i stayed in a 80 bath room ust to try at a guesthouse but it was quite horrible , felt like i was in a prison cell, so its worth put a little more bath in and get better standard.
Good luck!
Veronika