Bangkok's Koh Sahn Rd is often the starting point for trips in Asia for the backpacker crowd and it really is a good starting point to catch on the latest fashions that are on the backpacker scene lot of travel agents offering cheap flights to everywhere Great street stalls offering everything fro music to tattoos to fake degrees. you can eat on the street for under a dollar a day if you are so inclined. Lots of bars and banks and just a freaking menagerie that you really need to see at least once this is the best place in Bangkok for people watching if you are into looking at people from all over the world. the next best would be Pattaya walking street But you need to go to that page for that.
Bangkok Guesthouses on Koh Sahn rd generally don't need reservations and with the exception of the more expensive places like the Sawadee hotel chain, the Buddy Hotel group and the largest and the most popular for it roof top bar the D &D most maybe be will except but will not honor alot of times unless you have a relationship with them anbd they know you This not a hard fast rule but a good piece of advice to keep in mind so that you don't have a rude surprise at 2 am in the morning when your cheap flight from LA to Bangkok Arrives late.
If you get off of Koh Sahn rd proper and get into the area closer to the river you are going to find some very nice little guesthouses if you are facing towards the river head down the side of the wat there are any number of good cheap guesthouses in this area. another area to check is the if you are facing towards the river the block to the right there are some alleys that you can find that will take you through or go around the block these tend to be cheaper with Bangkok's cheapest Koh Sahn Guesthouse the Green House.