Cheap places to stay near bangkok airport?

I'm flying from Bangkok Suvarnabhumi Airport at 9am , arrive back in bangkok at 9pm the night before, can anyone rec a CHEAP place i can stay that night which is next to the airport? So i can land from Samui , sleep and go back to the airport quickly. Also can you tell me the best way to get from Bangkok Airport to the kho san road when i arrive? How much such a cab cost?? Should i pre book?