Buying next to undeveloped land: how to check what can legally be built beside your plot

Can a resort, a three-storey villa, or a fence wall legally go up on the vacant land next to the plot you're buying? The honest answer is: probably something can, and the only way to know what is to check the neighbouring parcel against the same four filters a buyer should apply to their own land — title class, zone, setback rules and project-scale triggers — before signing anything.

1. Check the neighbouring plot's title class

A chanote (full title) neighbour can build almost anything the zoning allows. A weaker title changes the picture: land held on Nor Sor 3 Gor is buildable but less precisely surveyed; land on Sor Kor 1 or PBT5/Sor Por Kor claims is agricultural-use paper that was never meant to authorise construction and often overlaps forest-reserve or national-park boundaries that can never be converted to chanote — see Untitled "sea-view land" scams. A neighbour on that kind of title is a double risk: it can attract an enforcement action that spills onto adjoining plots during a boundary survey, and if it later turns out to be reserve land, no legal structure can ever go up on it at all — which cuts both ways for your own view and your own risk exposure.

2. Check the neighbouring plot's eco-zone, not just yours

Since 22 May 2025, the Surat Thani provincial environmental protection notification covers the whole island with distance-from-shore and elevation-based building tiers — the same rules apply to the plot next door as to yours. A neighbouring coastal parcel within 10-50 m of the high-tide line is capped at a single storey, 6 m height and 75 m² floor area; beyond 200 m or above 80 m elevation, the caps loosen substantially. Pull the neighbour's exact distance-from-shore and elevation figures, not just your own — see Coastal setback rules on Koh Phangan and Hillside building limits for the full tier tables, and Island eco-zoning for how the zones fit together.

3. The setback law that governs distance to your boundary

Independent of zoning, the Building Control Act B.E. 2522 (1979) and its Ministerial Regulation No. 55 (B.E. 2543 / 2000) set fixed minimum distances between any structure and the property line, and these apply symmetrically — they constrain what a neighbour can build close to you just as they constrain you:

• A wall with windows, doors or balconies in a building over roughly 9 m tall must sit at least 3 m back from the boundary line.
• A blank wall closer than 3 m must be solid (no openings) and set back at least 50 cm from the line, with a parapet at least 1.8 m high where it faces the boundary.
• A wall built directly on the boundary line is allowed only up to 15 m in height and only with the adjoining landowner's written consent — meaning a neighbour cannot legally put a tall structure flush against your property line without your sign-off, and you can't do it to them either.

4. Whether a larger project would trigger a public hearing

A single private villa next door rarely gives you advance notice. A larger development does: a hotel or resort of 80 rooms or more, or with 4,000 m² or more of usable floor area, requires an Environmental Impact Assessment under the Enhancement and Conservation of National Environmental Quality Act, and the EIA process legally requires a public hearing before approval — a channel through which a neighbouring landowner can see, and formally comment on, what's being proposed next door. Smaller guesthouses and single villas fall below this threshold and file for a standard building permit at the District Office with no public notice requirement at all.

What to actually do before you commit

• Pull the title deed and its history for the neighbouring plot at the Land Office, the same way you would for the plot you're buying — title class, registered owner, and any mortgages or existing structures noted on the back.
• Ask the District Office (or a local lawyer) for the neighbouring parcel's coastal-distance and elevation figures under the 2025 zoning notification, not just its street address or general area.
• Check whether any building permit application is already on file for the adjoining plot — permit applications are public records at the District Office once submitted.
• Don't rely on "it's always been empty" as a substitute for checking the zone and title — vacant land on Phangan has filled in quickly in past building cycles, and the legal ceiling on what can go up there is set by paperwork, not by how the lot looks today.

None of this replaces walking the boundary with a surveyor and confirming physical markers match the title, covered in Due diligence before buying — but that checklist is about your plot. Extending the same rigor to the plot next door is what actually tells you whether the view, the quiet, or the setback you're paying for today is something the law protects, or something a future permit application can simply build over.