Measuring Thai Properties

Thailand's Measurement System. Its unique, where did the Rai, Ngan and Wa come from?

Where Did the Thai System Originate?

Like many ancient measurement systems, traditional Siamese units were based on human anatomy and agricultural labor. Long before electronic surveying tools, early Siamese farmers and rulers measured land by what a person could physically reach, walk, or cultivate.

• The Wa (Fathom): The fundamental building block of length was the Wa (วา), defined as the distance between the fingertips of an adult man’s fully outstretched arms—roughly 2 meters (similar to the Western fathom).

• The Rai (Agrarian Field): The word Rai (ไร่) literally translates to "farm," "field," or "plantation". Historically, 1 Rai represented the estimated area of land a farmer could plow using a team of oxen in a single day.

• The Ngan (A Day's Work): The word Ngan (งาน) literally means "work" or "task". In ancient Siam, 1 Ngan represented a manageable standard daily work allotment given to agricultural laborers.B. Land & House Ownership Restrictions

  The Standardisation of 1923

  For centuries, these units varied slightly depending on regional arm spans or soil conditions. However, on December 17, 1923, King Rama VI officially aligned Siam's traditional units with the metric system.

  Rather than abandoning the culturally embedded terms, the government standardized them onto an exact metric grid:

  • 1 Wa was codified as exactly 2 meters.

  • 1 Tarang Wa (Square Wa) became exactly 4 square meters (m²).

The Core Units of Measurement Explained

Thai land is measured across three primary hierarchy levels.

1 Rai = 4 Ngan = 400 Tarang Wa = 1,600 sq.m

└─── 1 Ngan = 100 Tarang Wa = 400 sq.m

└─── 1 Tarang Wa = 4 sq.m

A. Tarang Wa (ตารางวา) — Square Wa

• Size: 4 m² (approx. 43 sq. ft.)

• Usage: Used for small plots, building footprints, villa footprints, and suburban home land parcels. When land prices are quoted in urban areas like Bangkok or Phuket, they are frequently priced "per Tarang Wa."

B. Ngan (งาน)

• Size: 100 Tarang Wa = 400 m² (approx. 4,306 sq. ft. or 0.1 acres)

• Usage: Medium-sized plots, large residential garden plots, or small subdivisions.

C. Rai (ไร่)

• Size: 4 Ngan = 400 Tarang Wa = 1,600 m² (approx. 0.395 acres / 0.16 hectares)

• Usage: Large plots, housing developments, resorts, farms, and raw land holdings.

How to Read a Thai Land Title Deed (Chanote)

On official Land Office documents and real estate listings, land size is written as a three-number sequence separated by hyphens:

Rai - Ngan - Tarang Wa

Example: Reading a 2 - 1 - 50 Plot

If a villa listing states the plot size is 2-1-50, it breaks down as:

• 2 Rai = 2 x 1,600 m² = 3,200 m²

• 1 Ngan = 1 x 400 m² = 400 m²

• 50 Tarang Wa = 50 x 4 m² = 200 m²

• Total Land Area: 3,800 m²

Understanding Thai Land Measurements: History, Units, and Conversions

When exploring property or land in Thailand, foreign buyers often expect measurements in square meters, square feet, or acres. However, Thailand uses its own customary system of spatial measurement.

While condominiums are sold in standard square meters (m²), land and landed homes (villas, townhouses, plots) are bought, sold, and registered at the Land Office using Rai, Ngan, and Tarang Wa.

Understanding this system isn't just useful for reading a property listing—it offers a fascinating look into Thailand's agrarian history.