Rai, Ngan and Square Wah: Thai Land Measurement Units

Reviewed by ThaiLawOnline, a licensed Thai law firm practising in Thailand since 2006. Thai lawyer of record: Wichuda Atthamethakon, LL.M., Thai Bar Licence 3149/2556.

Last updated on September 5, 2026

Rai, ngan and square wah (ไร่ งาน ตารางวา, also written talang wa, sq. wah, wa or tarang wah) are the traditional Thai units of land area and the only units used on title deeds, in Land Office records and in the government appraisal lists. One rai is 1,600 square metres, one ngan is 400 square metres and one square wah is 4 square metres, so a rai is four ngan and a ngan is 100 square wah. A title deed states the area as three numbers separated by dashes, for example 1-2-32, meaning 1 rai, 2 ngan and 32 square wah.

How the units fit together

Everything is built on the wah. A wah is a length of 2 metres, so a square wah is 2 by 2 metres, or 4 square metres. One hundred square wah make a ngan (400 square metres), and four ngan make a rai (1,600 square metres). The metric equivalents are exact, because Thailand defined the wah as 2 metres when it adopted the metric system in 1923, so conversions never involve rounding.

Condominium units are the exception: the Condominium Act and unit title deeds use square metres, and the 49% foreign quota is calculated in square metres of unit area. Land under a condominium, like all land, is still recorded in rai, ngan and square wah.

Reading the area on a title deed

The area on a Chanote is the surveyed area, written on the front page in the three-number form and repeated in every registration on the back page. On a Chanote it comes from a ground survey with concrete boundary markers; on a Nor Sor 3 Gor from an aerial survey; on a Nor Sor 3 it is an estimate. The number on the deed governs, not the agent’s brochure and not what a walk around the fence suggests.

Land prices are quoted per rai in rural areas and per square wah in towns and resorts, so a plot advertised at 30,000 baht per square wah costs 12 million baht per rai. The government appraised value used for transfer fees is published per square wah, and the Land Office multiplies it by the deed area to fix the fee base.

The common mistake is to convert loosely. Reading 1-2-32 as “about one and a half rai” ignores 128 square metres, and on a beachfront plot at 100,000 baht per square wah that error is worth 3.2 million baht. A second mistake is to treat the rai as a fixed fraction of an acre; it is roughly 0.4 acre, which is fine for conversation but not for a contract.

When the deed area and the ground disagree

Older deeds, and deeds converted from Nor Sor 3, sometimes state more or less land than the boundary markers enclose. A buyer who wants certainty can ask the Land Office for a re-survey before the transfer; the officer locates the markers with the neighbours present and corrects the deed if needed. Where land is later found short, the buyer’s claim against the seller depends on whether the contract sold a stated area or a plot “as is”, so the sale agreement should say which and should price the land per square wah if the area matters.

Sub-division and consolidation are also expressed in these units. A plot of 2-0-00 split into four parcels of 0-2-00 each becomes four deeds of 800 square metres, and the Land Office charges its survey fee per parcel. The guide on measurements in Thailand covers the other traditional units still met in building and construction contracts.

Frequently asked questions

See also: Chanote (Nor Sor 4 Jor), Appraised value, Land Office, Nor Sor 3 Gor, How to Read a Title Deed in Thailand and Measurements in Thailand.