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Land measurement in Thailand operates within a unique framework that combines traditional units of area with modern cadastral surveying techniques. For anyone considering purchasing property, developing land, or resolving boundary disputes, understanding this system is essential. Thailand does not use the imperial or metric systems for land area; instead, it relies on traditional units that are legally defined and strictly regulated by the Department of Lands (DOL) under the Ministry of Interior . This article provides a comprehensive, in-depth examination of land measurement in Thailand, covering the foundational units, their relationship to different title deeds, the surveying process, common disputes, and practical guidance for navigating this critical aspect of property ownership.

The Legal Foundation: Traditional Thai Measurement Units

The Thai land measurement system is governed by the Land Code Act B.E. 2497 (1954) and subsequent regulations, which define the precise relationship between traditional units and the metric system . Although Thailand adopted the metric system in 1923, land area continues to be recorded using the traditional units of Rai, Ngan, and Square Wah (Tarang Wa) . These units are legally defined in exact metric equivalents, ensuring consistency across all official documents.

The foundational unit is the Wah, a linear measurement equivalent to exactly two meters. From this, the Square Wah (Tarang Wa) is derived as the basic unit of area: one square wah equals four square meters . This forms the basis for all larger units:

1 Square Wah = 4 square meters

1 Ngan = 100 Square Wah = 400 square meters

1 Rai = 4 Ngan = 400 Square Wah = 1,600 square meters

For international comparison, one hectare equals 6.25 Rai or 10,000 square meters, and one acre equals approximately 2.5 Rai or 43,560 square feet .

In official documents, land area is typically written in the format Rai-Ngan-Square Wah. For example, "2 Rai, 3 Ngan, 25 Square Wah" represents a total area of 3,300 square meters (calculated as: (2 × 1,600) + (3 × 400) + (25 × 4) = 3,200 + 1,200 + 100 = 3,300 m²). Some government documents discourage using hyphenated numerical formats like "2-3-25" to avoid misinterpretation, though this notation remains common in practice .

Title Deeds and Measurement Accuracy

The accuracy and legal reliability of land measurements depend critically on the type of title deed held for the property. Thailand's land documentation system features a hierarchy of titles, each with different surveying standards .

Chanote (Nor Sor 4 Jor)

The Chanote represents the highest and most secure form of land title. It is based on GPS-surveyed coordinates with permanent boundary markers (หลักเขต, lak chet) physically set in the ground at each corner . The survey accuracy is within ±1-2 centimeters, and the measurements are legally precise and enforceable . Chanote titles include detailed cadastral maps showing exact boundaries, plot numbers, and adjacent land references . For buyers, a Chanote offers the clearest protection against measurement disputes.

Nor Sor 3 Gor

This title grants strong ownership rights and includes land that has been officially surveyed by the Department of Lands, with recorded boundaries . However, Nor Sor 3 Gor titles are not based on GPS coordinates with permanent markers, so boundary accuracy is slightly less precise than a Chanote . The land may be sold, transferred, or mortgaged, and owners can apply to upgrade the title to a Chanote through a formal resurvey process .

Nor Sor 3

The Nor Sor 3 title confirms possession but does not include precisely measured boundaries. The land has never been formally surveyed by the Land Department, so boundaries are described textually rather than mapped with precision . This creates significant risk of boundary overlaps and disputes with neighboring landowners . Selling or transferring Nor Sor 3 land requires a 30-day public notice period to allow objections, and the area stated on the deed may not match ground reality .

Sor Kor 1 and Possessory Rights

These documents represent the lowest tier of land documentation. They are not issued by the Land Department but rather recognized through tax payments at the Local Administrative Office . Sor Kor 1 provides no reliable measurement or legal enforceability and cannot be sold or transferred through the Land Office . Extreme caution is advised when encountering these titles, as they are unsuitable for standard property transactions.

The Surveying Process and Professional Roles

Land surveying for official purposes is strictly regulated by the Department of Lands. Only certified DOL officers can conduct measurements that carry legal weight for title registration .

Application and Field Survey

The process begins with filing an application at the local Land Office where the property is located, accompanied by the original title deed and owner identification . DOL surveyors then visit the property with specialized equipment including total stations and GPS/GNSS tools. They locate existing corner posts or plant new ones, often with adjacent landowners invited to witness the survey .

Mapping and Registration

Following the field survey, a sketch map (rubthang) is prepared and attached to the title deed, showing the plot number, area, adjacent plots, and road access . For subdivisions or consolidations, the Land Office posts a 30-day public notice to allow objections before updating the title deed with the new measurements .

Professional Roles

Only licensed DOL-certified surveyors can conduct official measurements for title registration. Private surveyors, engineers, or architects may conduct measurements for planning, construction, or valuation, but these results have no legal weight unless certified by the DOL . Property lawyers play a crucial role in advising clients on boundary disputes, reviewing title documents, and ensuring that measurement-related clauses in contracts are properly drafted .

Common Measurement Disputes and Legal Remedies

Disputes frequently arise when the measured area on the ground differs from that stated on the title deed, when boundary markers are missing or displaced, or when neighboring landowners encroach onto each other's land .

Overlapping Boundaries and Encroachment

Overlapping boundaries are common with Nor Sor 3 and Nor Sor 3 Gor titles, especially in rural areas where surveys may be based on old manual sketches rather than precise measurements . Encroachment occurs when adjacent landowners have built structures over boundary lines, requiring resurvey and potentially court intervention to resolve .

Discrepancies Between Title and Physical Area

The title may state a specific area, but actual land size may differ. Thai courts generally favor the title deed's surveyed area, particularly for Chanote titles, unless strong evidence of error or fraud is presented . However, physical possession patterns may influence dispute outcomes in some cases.

Remedies and Resolution

Property owners facing measurement discrepancies may submit a request for land resurvey at the Land Office, file a complaint with the Land Inspection Division, or utilize the land adjudication process (พิสูจน์สิทธิ์ในที่ดิน) in cases of overlap . If these administrative remedies fail, a civil lawsuit may be necessary to determine ownership or establish correct boundaries.

Digital Transformation and Modernization

The Thai government is advancing the Land Information System (LIS) to digitize land records and integrate GIS mapping tools . This modernization aims to eliminate duplicate or overlapping titles, provide online access to cadastral maps, facilitate efficient land transactions, and increase tax compliance under the Land and Building Tax Act .

However, only Chanote titles are currently fully compatible with these digital systems. The integration of GNSS-based technologies and aerial drone mapping is gradually improving the accuracy and reliability of land measurement data .

Practical Guidance for Buyers and Investors

For anyone considering property acquisition in Thailand, several practical steps are essential:

Verify title deed type before proceeding with any transaction. Chanote titles offer the highest security; extreme caution is warranted for lesser titles.

Commission a licensed surveyor to verify that physical boundary markers match the title's coordinates and cadastral map .

Check for encumbrances through a formal title search at the Land Office, including mortgages, leases, easements, or court orders .

Confirm zoning and land use regulations with municipal authorities to ensure intended development is permitted .

Include measurement provisions in contracts specifying responsibility for area discrepancies and procedures for remeasurement if needed .

Conclusion

Land measurement in Thailand operates within a sophisticated legal framework that combines traditional units with modern surveying techniques. The Rai-Ngan-Square Wah system, precisely defined in metric equivalents, appears on all official title documents and governs property transactions throughout the Kingdom. Understanding the hierarchy of title deeds—from the gold-standard Chanote with GPS-surveyed boundaries to the precarious Nor Sor 3 with unmeasured borders—is essential for interpreting measurement accuracy and legal reliability.

The survey process, strictly regulated by the Department of Lands, ensures that official measurements carry legal weight, while private surveys serve planning purposes only. Measurement disputes, whether from boundary encroachment or title discrepancies, require systematic resolution through administrative channels or court proceedings. As Thailand continues its digital transformation of land records, the reliability and accessibility of measurement data will only improve. For buyers and investors, engaging qualified legal and surveying professionals to verify measurements before committing to any transaction remains the surest path to secure property ownership in the Kingdom.