There is an instrument called a USUFRUCT. This is a very old law (originating from the Romans), that Thailand adopted from the west. It is pretty useful and works like this:

The owner of the land can sign over the land using the USUFRUCT. It is still owned by the original owner, but the USUFRUCTEE has full rights (except the ability to sell it) over the land. They can build, own the buildings, own any produce from said lad (Mangos etc) and treat it as their own land pretty much. The USUFRUCT can only be cancelled by both parties under agreement (they are registerd with the courts, so are legally binding) or by the death of the USUFRUCTEE - they are not inheritable, but children can also be added. This can bne betwelen man and wife etc.
This can be done free without any taxes etc if the USUFRUCT is not charged for (if the owner is a business, there is expectation of a charge for the USUFRUCT to inhibbit fraud - tax is payable then - though its low). There is real need for lawyers as it needs to be registered etc. There are companies (PM me and I'll give you the name of the person I am using - for more details) that do everything for you - the land registry dept always want to talk you into renting/leasing the property insead. Why? Because it generates tax and is revokable - your lawyer/agent will push all that aside as they know the law and your rights etc. The Agency costs between 10k and 20k on average - depending where in the country you are. Out of town areas and the boonies often do not have land regisrty offices or the land is not title deeded etc, this costs more as the travelling ibetween offices may be greater (may well be in different towns!) - this is why the price variance.

By the way - as the USUFRUCTEE, you can not be turned off the land (other than by the government - compulsory buying etc) - and can even kick the land owner off. It lasts until the last USUFRUCTEE dies. The owner can sell it, but the USUFRUCT goes with the purchase, so no change tot the USUFRUCTEE (and nobody wants to buy land with an open USUFRUCT on it - so if you do want to sell at some point, make the USUFRUCT cancellation a point of the sale).