Most of the people in here probably already knows everything when it comes to renting scooters in Thailand. But for those who don't know, here is some information you might find helpful.
Many rental shops wants you to put your passport as deposit, but if you bring back the scooter and the rental shop claims that you scratched or broke something on the scooter you will not have your passport back until you have paid. Take a photocopy of your passport or give them a small cash deposit instead. If they don't agree to this just choose another shop, there are many of them.
Bring a camera and take as many photos as possible from every angle of the scooter, this is to prevent anyone to blame you and want you to pay money for a damage you didn't do.
Read through the rental contract careful before signing, sometimes they want a lot more money from you if the scooter gets stolen than a new scooter actually cost.
Check out the helmets as well, look for cracks. Make sure you get two as the law here requires that both the driver and passenger wears a helmet. And WEAR the helmets, the police love pulling over tourist and hand them a fine. And by a new law here in Thailand the police can even force you to stay i the police station and watch a movie WHY you should wear a helmet.
Thai law requires you to have an IDP (International Drivers Permit) when you drive in Thailand. However if you get pulled over by the police a "normal" driving licence will be enough.
If you don't have any driving licence it's better you don't rent. if you have an accident without a driving licence you might be i big trouble.
Maybe i left something out, but i hope someone got something out of it.
Drive careful.....