The seller's warranty against eviction: what happens when someone else's prior right surfaces after you buy

You've registered your purchase, moved in, and months later someone shows up with an old, undisclosed claim over the property — a lease the seller never mentioned, a construction lien, a neighbour asserting an access servitude, or someone claiming years of adverse possession. Can you hold the seller responsible? Under CCC Sections 475–479, generally yes — Thai law makes a seller liable for disturbing your peaceful possession through a third party's prior right, a separate warranty from the physical-defect liability already covered for structural problems.

The core warranty

• Section 475 — the seller is liable for the consequences of any disturbance to the buyer's peaceful possession caused by a person holding a right over the property that already existed at the time of sale, or caused by the seller's own fault.
• Section 476 — the exception: the seller isn't liable for a disturbance caused by a right the buyer already knew about at the time of sale. A disclosed lease, a disclosed servitude, or anything the buyer had actual notice of doesn't trigger this protection.
• Section 479 — the warranty extends to full or partial eviction from the property because of a pre-existing right, and to a right that isn't strong enough to evict the buyer outright but still materially reduces the property's value, fitness for its intended purpose, or usefulness.

The procedure if a third party actually sues

Sections 477 and 478 give this warranty real practical teeth. If a third party brings a claim asserting a prior right over the property, the buyer can summon the seller to appear in that same lawsuit as a co-defendant or co-plaintiff, so the underlying ownership/rights dispute and the buyer's claim against the seller get resolved together rather than in two separate cases. The seller can also choose to intervene independently to fight the third party's claim directly, since a seller who successfully defeats the claim protects themselves from liability to the buyer too.

How this differs from the other warranties already on this site

• Not the same as physical-defect liability. Seller liability for property defects (CCC Sections 472–474, with the 483–485 "as-is" carve-outs) covers the physical condition of what you bought — cracks, a bad roof, a failing septic system. Sections 475–479 cover legal disturbance of your title or possession by someone else's right, an entirely separate warranty channel with its own rules.
• Not the same as the double-sale priority rule. The good-faith registered-buyer rule (CCC Sections 1299–1300) decides who keeps the land when a seller deals with two buyers. This warranty applies after that question is already settled — it's about what you can claim from your seller once someone else's right disturbs the possession you already hold.
• Doesn't undo a winner's title. Just as in the double-sale scenario, this warranty gives you a claim against the seller — damages, and depending on the severity, rescission — not a way to reverse a third party's superior, validly established right to the land itself.

On Koh Phangan specifically, this warranty is the buyer's civil-law backstop against exactly the kind of undisclosed prior claim the island's due-diligence checklists exist to catch in advance — an unregistered lease still binding for its first term, a neighbour's servitude, a builder's lien, or someone quietly building an adverse-possession claim on an unfenced corner of the plot. Good due diligence before signing is always cheaper and faster than relying on this warranty afterward, but it's a meaningful protection when something genuinely wasn't discoverable — or wasn't disclosed — at the time of sale.