Foreign individuals cannot hold Thai land freehold. Villa purchases are therefore structured either as a registered lease of the land, or through a Thai company that holds it — and the choice has consequences that outlast the purchase.
Registered leasehold
A lease of up to thirty years is registered against the title and is enforceable. Renewals beyond that are contractual undertakings rather than registered rights. Leasehold is simpler to hold and cheaper to run, and its value declines as the term shortens — which is why the remaining term, not the original one, is what a resale buyer prices.
Company ownership
A Thai company may own land outright. The company must be genuinely constituted and operated; structures relying on nominee shareholders are not lawful, and the risk sits with the buyer.
Company ownership carries ongoing accounting and filing obligations, and on resale you are selling shares rather than land, which narrows the buyer pool.
Neither structure is inherently better. Which one suits depends on the holding period, whether the property will pass to family, and how the eventual sale is expected to happen.