YOu need to go to the transport office where you live and get it transfered there - you will need your
1)WP (if you have one)
2) a letter from your embassy or immigration stating that you live at your address (use immigration they are cheaper).
3)two copies of the transfer papers completed and signed by the owner plus
4) two copies of his "Tabian Ban" (house registration) and
5) two copies of his ID card signed.
6) Two copies of your passport showing visa,
7) any other ID you might have two copies of signed
A Thai person is always handy to have as well generally you don't need to sign them or make two copies of them either.
Then some good luck - they might help you transfer it they might just sit and stare at you.
If its a small bike and you know a native that you trust then get it in their name - not you g/f's or b/f's
If not do you really need to worry about changing owners - if you have the previous owners book and transer papers just use it in their name - you can still tax it and insure it no problem.
Any more questions feel free to ask