Before any Thai land purchase or development project pencils out, the plot's zoning color code, Floor Area Ratio (FAR) and Open Space Ratio (OSR) determine what can legally be built there — and by how much. Here's how the color-coded comprehensive plans work, how FAR and OSR are calculated, how the rules shift between Bangkok and other provinces, and how to verify the real numbers for a specific plot before you commit. General information only, never legal or tax advice.
Every plot of land in Thailand sits inside a color-coded zone set by a local comprehensive plan (ผังเมืองรวม), which caps how much you can build via Floor Area Ratio (FAR) and how much open ground you must keep via Open Space Ratio (OSR). Rules vary by municipality — Bangkok's plan is denser and more detailed than most provincial plans — so always confirm the current figures for the specific plot, not a rule of thumb from elsewhere.
Thailand's land-use zoning runs on comprehensive plans adopted under the Town and City Planning Act. Each plan is a color-coded map dividing a municipality or province into land-use zones — residential, commercial, industrial, agricultural, conservation and so on — each with its own permitted-use table, density caps and building restrictions. In Bangkok, the plan is drafted and administered by the Bangkok Metropolitan Administration (BMA). Elsewhere, provincial and municipal plans are typically developed with the Department of Public Works and Town & Country Planning (DPT) and adopted at the local level. Plans are intended to be reviewed on a roughly five-year cycle, though revisions frequently run late — when a plan technically expires before its replacement is adopted, interim or carried-over rules commonly continue to apply, which is exactly the kind of detail worth confirming with the local planning office rather than assuming.
Colors are the fastest way to read a zoning map, but the exact permitted uses and limits behind each color are set out in a separate use-table — the color alone is a starting point, not the full rule:
Sub-categories (e.g. yellow-1 vs yellow-2, or a "-ก/-ข/-ค" style suffix) can carry meaningfully different density and use limits within the same base color, and the exact palette and sub-codes differ between Bangkok's plan and provincial plans. Always read the plan's own legend and use-table rather than assuming a color means the same thing everywhere.
FAR expresses the maximum total building floor area allowed relative to plot size, as a ratio such as 3:1, 6:1 or 10:1. A FAR of 3:1 on a 1,000 sqm plot permits up to 3,000 sqm of total gross floor area across every level of the building — spread as a low, wide structure or a taller, narrower one, subject to separate height, setback and parking rules. In most comprehensive plans, FAR rises with zone density (commercial and high-density residential zones carry the highest ratios) and with proximity to BTS/MRT stations, since many plans include a transit-oriented-development FAR bonus for land within a set radius of a station entrance. FAR falls sharply in low-density residential, agricultural and conservation zones. Because FAR directly caps the sellable or leasable floor area a project can deliver, it is usually the single most important number in a development feasibility study — always verify the current, plot-specific FAR rather than relying on a nearby project's density as a proxy.
OSR sets a minimum share of the plot (or, under Building Control Act rules, sometimes of usable floor area for certain building types) that must stay as open space — landscaping, setbacks, courtyards or permeable ground rather than building footprint. It works together with FAR, not instead of it: FAR caps total buildable area, while OSR and building-type-specific requirements under the Building Control Act (which differ for residential, hotel, office and factory buildings, among others) constrain how that floor area can be packed onto the site, and how much green space, stormwater drainage and fire-truck access must be preserved. A design can hit its full FAR allowance on paper and still fail to comply if it doesn't leave enough open ground — feasibility studies need to check FAR and OSR together, alongside height limits, setbacks and parking-ratio requirements, before treating a project as buildable.
Bangkok's comprehensive plan, administered by the BMA, is among the most detailed in the country — dense sub-zoning, explicit station-area FAR bonuses along BTS and MRT lines, and frequent public consultation on revisions. Other provinces and municipalities each adopt and periodically revise their own plans, generally with simpler zoning structures and lower density caps that reflect local development pressure. Coastal and tourism-driven provinces — Phuket, Pattaya/Chonburi, Hua Hin and others — often layer on additional overlay restrictions such as building-height limits near beaches or heritage conservation zones. The Eastern Economic Corridor (EEC) provinces (Chonburi, Rayong, Chachoengsao) carry their own EEC-specific land-use and industrial-zoning framework on top of standard municipal plans, tied to BOI and EEC investment promotion. The practical takeaway: a zoning color or FAR figure that applies in central Bangkok tells you nothing reliable about the equivalent zone in a provincial town — always pull the specific municipality's current, in-force plan.
Zoning, FAR and OSR aren't background paperwork — they set the ceiling on a project's revenue potential before a single design drawing is made. FAR determines the maximum sellable or leasable floor area a plot can produce, which drives the entire project pro forma: unit count, construction cost per sellable sqm, and ultimately return on the land price paid. OSR, height limits and setbacks then determine whether that FAR is actually achievable in a buildable massing, or only on paper. Buying land — or agreeing a price — based on an assumed FAR that turns out to be lower than expected (or discovering the plot sits in a zone that doesn't permit the intended use at all) is one of the most common and expensive mistakes foreign investors and first-time developers make in Thailand. Confirming zoning, FAR and OSR should happen before a deposit is paid, not after.
BAANLYY can help you find a licensed Thai architect, engineer or land-use consultant to verify buildability before you commit.
General information only — not legal, tax or engineering advice. Zoning color codes, Floor Area Ratio, Open Space Ratio and related limits in Thailand vary by municipality, are revised periodically, and can change without notice; always verify the current, plot-specific figures with the BMA, the relevant provincial or municipal town-planning office, or a licensed Thai architect, engineer or lawyer before relying on them. BAANLYY never takes paid placement in editorial content.
Primary and official sources are cited above. Government rules, fees and procedures in Thailand change over time and vary by office; always confirm current requirements with the relevant authority before relying on them. BAANLYY never takes paid placement in editorial content.