Where can I find a place to rent a motor scooter in Bangkok, Thailand?

Have you been to Bangkok and seen the way they drive cars and motorcycles here. I would think twice about it unless you been here before and know the Thai way of following traffic laws.

if u move around a little u will find plenty of places that hire mo bikes

There are hundreds of places. You need to show passport, pay a deposit and show licence at any decent shop. If you go with a Thai Guide, they will get 40% less on the hire fee, unless your great at bartering in Thai.
Why would you want to hire one? Taxi and tuk tuk are cheap and you dont have to worry about riding or parking the thing? Great to feel and smell the breeze in your face, but the biggest risk of injury for Farang foreigners is from motorcycle injury.
If your going up country then I would hire it, when you arrive at your destination.

lol... on every corner

You can hire a bike almost anywhere in Thailand, there are outlets on every street corner.

You will need your passport and license.
Cost can vary, last year I paid 200 Baht per day, can be cheaper if you shop around and barter.

Cross roads are deadly, railway lines are suicidal, and speed will kill you.

My opinion is the bike is the easiest and cheapest way to get around and see what "you" want to see in your own time.

I always hire a bike when i am there, a 125 Yamaha, and thats what I use to get holiday freedom.

Take my advise....WEAR YOUR CRASH HELMET, and have fun.