We hired a scooter from George (swiss) at VJ plaza (north of Klong Prao). What a helpful guy. He supplied us with a nearly new scooter and helmets (now the law). We hired it for almost 2 weeks at 200baht a day.
We left a 3000baht deposit, otherwise he asks for some form of I'd to be left as security.
I am always a bit anxious about hiring from street side vendas, but this guy is excellent. Take the time to have a fab authentic pizza opposite his shop if you have the time.