As a foreigner staying in Thailand, you should prepare:
(a) a copy of your passport (photo page)
(b) a copy of the visa page in your passport and
(c) a copy of the departure card (or write down the number on the copy of your passport)
The landlord should prepare:
(a) a copy of the title deed of the property
(b) a copy of the rental contract
In case the landlord has outsources this matter to a property manager, a letter is needed giving authority to this property manager to report TM30 on behalf of landlord with stamps from the tax office on this letter.