Land Measurement in Thailand. Thailand’s land measurement system is unique, built upon traditional units that are still in active legal and transactional use today. While the metric system is officially adopted in many aspects of Thai governance, land measurement remains firmly rooted in traditional Thai units, creating the need for accurate conversions and a deep understanding of cadastral surveys, title documentation, and real-world boundary enforcement.
This article explores the legal framework, unit system, surveying practices, title deed correlation, and common problems arising in land measurements in Thailand.
In Thailand, land is measured using a system that dates back centuries. While Thailand is a signatory to the metric system, land continues to be measured in:
| Thai Unit | Equivalent in Metric | Notes |
|---|---|---|
| 1 Wah² (ตารางวา) | 4 m² | Basic unit |
| 1 Ngan (งาน) | 100 Wah² = 400 m² | Used for medium plots |
| 1 Rai (ไร่) | 4 Ngan = 1,600 m² | Primary unit for land |
For larger areas, land size is usually quoted in Rai-Ngan-Wah² format. For example, a parcel of 3 Rai, 2 Ngan, 50 Wah² is equivalent to:
(3 × 1600) + (2 × 400) + (50 × 4) = 6,600 m²
These units are legally recognized in all land title deeds, court filings, tax assessments, and official transfers.
Although not officially used in property law, metric units such as square meters (m²) and hectares (ha) are often provided for reference—particularly in:
Foreign contracts
Condominium unit sales
Surveyor reports
However, land title deeds always list size in traditional units, and conversion is advisory. Accurate conversion is essential when dealing with mixed-unit measurements.
| Metric Unit | Thai Equivalent |
|---|---|
| 1 m² | 0.25 Wah² |
| 1 hectare | 6.25 Rai |
| 1 acre | Approx. 2.5 Rai |
Land measurement and registration in Thailand are regulated by the Land Code B.E. 2497 (1954), supplemented by:
Ministerial Regulations
Department of Lands (DoL) practices
Cadastral Survey Manuals
The Department of Lands, under the Ministry of Interior, is responsible for:
Maintaining the official cadastre
Issuing and updating land titles
Approving survey records
Overseeing boundary conflicts and verifications
All title documents—such as Chanote, Nor Sor 3 Gor, and Nor Sor 3—include stated land size, boundaries, neighboring plot numbers, and survey reference points.
Thailand has gradually transitioned from traditional compass-and-chain measurements to modern GPS and digital cadastral mapping.
Graphical Survey (older titles)
Based on physical measurement from landmarks and chains, often found in Nor Sor 3 titles. Subject to inaccuracies.
Photogrammetric Survey
Using aerial photography overlaid with physical data. Offers better accuracy and is used in updating Nor Sor 3 Gor titles.
GPS-based Triangulation Survey
Used in issuing Chanote titles (Nor Sor 4 Jor). Offers high precision with error margins below ±5 cm.
Permanent boundary markers (Lak Chet) are used in Chanote plots. Their exact positions are legally binding and can be located using survey maps.
Most secure title
Fully surveyed with GPS
Clear area measurements and markers
Suitable for land transfer, mortgage, subdivision
Moderately accurate
Surveyed but not fully triangulated
Area is reliable, but boundaries can shift slightly
Hand-drawn surveys
Subject to overlaps and estimation errors
Used in rural or developing areas
Not formally surveyed
Meant for agricultural land or state leases
May be upgraded to full titles via adjudication
Each title specifies land size in Rai–Ngan–Wah², but accuracy and enforceability differ by title type.
Common causes of land measurement disputes in Thailand include:
Overlapping boundaries in Nor Sor 3 or Gor titles
Missing or displaced boundary markers
Topographical changes, such as river movement or erosion
Surveyor errors in older plots
Discrepancy between physical and registered measurements
In case of disputes:
The Land Office may conduct a resurvey
A land adjudication process (พิจารณาสิทธิ) may be initiated
Courts can be petitioned to determine boundaries based on title documents, witness testimony, and physical evidence
Legal resolution can take months or years, especially if neighboring titles are affected.
Subdividing a land plot for sale or development (e.g., housing estates) requires:
Precise re-survey
Issuance of new Chanote titles
Minimum plot size compliance (depends on zone)
Road and utility servitudes properly measured
Developers often hire licensed surveyors to submit plans to the Land Office, which must approve subdivisions and adjust the master map accordingly.
While condominium units are measured in square meters, the land on which the condo sits is still measured in Rai–Ngan–Wah².
The ratio of ownership in the common property (land and facilities) is derived from the total floor area of all units vs the individual unit size.
Foreigners purchasing condos must understand:
The foreign quota (49% of total sellable space)
The land area ratio, which affects voting rights and responsibilities
The entire land plot’s measurement, relevant for future redevelopment or legal claims
Thailand has launched projects to modernize its land records:
Land Information System (LIS): Integrates cadastral data, title records, and GIS mapping
Digital survey archives: Provide online access to registered land surveys
Geospatial overlays: Used in zoning, taxation, and planning
This aims to reduce fraud, increase transparency, and improve land management—but implementation remains regionally uneven.
Always verify the land size stated in title deeds vs actual surveys.
Engage a licensed surveyor for independent measurement, especially on older Nor Sor titles.
Understand that Chanote land is safest for transactions requiring precise boundaries.
When converting from m² to Thai units, use accurate formulas and avoid rounding errors.
Ensure any subdivision or land adjustment is formally registered at the Land Office with updated mapping.
Understanding land measurements in Thailand is fundamental for secure property transactions, proper development, and legal certainty. The continued use of traditional Thai units in a modern legal context requires precise knowledge of conversions, title types, survey standards, and regulatory enforcement.
From the investor purchasing a villa on leased land to a real estate developer mapping a new project, a clear grasp of how land is measured, recorded, and verified in Thailand is crucial. Whether acquiring, leasing, subdividing, or resolving a boundary dispute, all parties must respect the intricate intersection between historical systems and current legal practice.