As I understand it, legally the land belong to someone else and the occupier/poster leases the land.
It has been a while since I was in Thailand, but it used to be the case that a lease of land was a personal right that terminated on the death of the leasee. As such, you cannot "will" this lease to another. Only the landowner can transfer the legal title to the beneficiary.
If this is still the case, then this whole thread is rather a waste of time.