Your beachfront plot's coastline moved: alluvion, accretion and Thailand's public-foreshore rule

If sand naturally builds up along a beachfront plot on Koh Phangan, does the owner automatically own the new strip of land? Often yes — but only under specific conditions, and only up to the line where Thai law says private ownership simply cannot reach. Two provisions of the Civil and Commercial Code sit in tension here: Section 1308 hands a riparian or coastal landowner the accreted land that naturally forms against their title, while Section 1304 puts the foreshore itself in the state's public domain, off-limits to private title no matter how the coastline shifts.

Alluvion: Section 1308

Section 1308 states plainly: "Where land is formed by alluvion, it becomes the property of the riparian owner." This is the general rule for land gradually and naturally built up by water action against an already-titled bank or shore — the new land simply attaches to the existing title without a separate registration act being strictly required, though in practice a landowner will still want the Land Office to survey and formally record the addition. The key word is natural: land created by dumping fill, building a seawall to trap sediment, or other artificial reclamation is a different legal question entirely and generally does not fall under this automatic rule — reclamation of state waterways or foreshore typically requires separate government permission and can result in state, not private, ownership.

Foreshore is public domain, regardless of how it got there

• Section 1304 defines the state's public domain (sap-sin sathārana) to include land reserved for the common benefit of the public — expressly naming foreshores, waterways, highways and lakes alongside land abandoned or reverted to the state.
• Section 1305 — public domain property is inalienable except by a specific law or royal decree; nobody can simply buy, sell, or be granted title to it.
• Section 1306 — no length of possession, however long, can establish a private claim (prescription/adverse possession) against public domain property.
• Section 1307 — public domain property cannot be seized, whether for debt or otherwise.

Put together, these sections mean the beach itself — the tidal foreshore used by the public — stays public domain even as its physical location shifts with erosion and accretion over the years. Newly accreted sand can, in principle, become private land under Section 1308 when it forms against an existing valid title; but land that is, or remains, classified as public foreshore for common use never converts to private ownership just because someone occupies or builds on it, and no amount of time changes that under Section 1306.

Koh Phangan's Laem Son Beach: the tension in real life

Reporting in September 2026 on Koh Phangan's Laem Son Beach shows exactly how contested this line can get. The beach was once a mining concession; after mining ended more than 30 years ago, sand naturally deposited along the shore expanded the beach from roughly 12.8 hectares to about 19.04 hectares — accretion in the Section 1308 sense — while local operators gradually built structures on it. The land is officially classified as public land for common use, and an estimated 13-14 operators currently occupy it without valid land title documents, despite some holding ordinary business registrations. A former sub-district mayor won court rulings against the structures years ago that were never effectively enforced, and the dispute has drawn calls for a wider anti-corruption investigation into land, construction and nominee-business practices on the island. It's a live illustration of why accreted coastal land can't simply be claimed by whoever occupies it first, and why the government retains — via Land Code Section 61 — the power to refuse or cancel any title purporting to privatise it.

What this means for a beachfront buyer

• Don't assume a beachfront boundary is static. A title's cadastral map reflects the shoreline at the time of the last survey; erosion can shrink usable land, and accretion can create adjacent land that isn't automatically yours just because it borders your plot informally.
• "Extra" land needs a formal process, not a fence. Any genuinely accreted strip still needs the Land Office to survey and record it as an addition to your title before it's safely yours — informally extending a wall or building onto new sand doesn't secure ownership and can create exactly the kind of encroachment problem enforcement crackdowns target.
• Setback compliance moves with the coastline. Coastal setback rules are measured from the current shoreline, so a shifting coast can change what's buildable on a plot even when nothing about the paper title has changed.
• A public-use classification doesn't disappear with occupation. Land mapped as public foreshore or common-use beach stays that way regardless of how long informal structures have stood on it, per Section 1306 — a fact that has repeatedly surprised long-term occupiers when enforcement finally arrives.

None of this replaces a proper survey: before buying or building on any Phangan plot with beach frontage, have a licensed surveyor and lawyer confirm the current, officially recognised shoreline and boundary against the cadastral map as part of standard due diligence — the same care that applies to verifying a title's history near forest or park boundaries applies just as much to a boundary that moves with the tide.