Hi, I want to buy a second hand motorbike in Thailand and put my name on the registration green book. Problem is I don't have a Thai work permit or own a house in Thailand as I work in Laos Monday - Friday and live in Thailand with my Thai family on the weekends, (we're not married). My Thai grandad will sign a lease agreement to say I stay with him and provide his Thai card etc. Will this be sufficient?  Does anyone know what the requirements are for a foreigner to change the motorbike registration book into their name? Any advice is greatly appreciated. 

I think you need your name to be registered in a thai house book (tabian baan) which isn't always as straight forward as it should be.

Most DLTs will accept a resident certificate from immigration, or a stat declaration stating your address from your consulate, or a yellow book. Ask at your local DLT as they sometimes have differing requirements.

Take lease agreement [& passport sized photos] to Immigration for Residency Certificate then off to Land Transport Office with seller, greenback in-hand & passport & seller's Thai IDs.

Thank you all for your advice, very helpful 

Would it be the same if I was to buy a new motorbike? 

Just give resident certificate to dealer.

They do all else for you.