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wah [Thai. วๅ]

In Thailand, at least as early as the 17ᵗʰ century – 20ᵗʰ century, a unit of length, the fundamental unit in Thailand's system of units of length. Since the standardization of 1923 = 2 meters (about 78.74 inches)¹. Also romanized as wa, wha, voua, vöuá and vouah. Abbreviation, w.

Between the latter half of the 19th century and 1923, the wah was 80 inches (2.032 meters). The prototype was a silver bar bearing two scratches, the distance between them being 1 wah. In 1876, this prototype was examined by the Standards Department of the British Board of Trade and the distance determined to be 79.999 inches.² Interestingly, Siamese law specified that the temperature at which prototypes represented their unit was 85° Fahrenheit, a sensible choice for a tropical country.

Before the 80-inch definition, the wah was about 1.922 meters.

1. United Nations, 1966, and by the Weights and Measures Act B.E. 2542 (1999).

2. W. A. Browne, 1879.

sources

Deux Ken valent une brasse qu'ils appellent Voüà, & qui vaut à peu prés un pouce moins que nôtre toise: si bien qu'il s'en faut tres-peu de chose que leurs huit grains de ris, qui sont leur doit, ne vaillent 9. de nos lignes que nous estimons égales à 9. grains d'orge.

Two ken make a brasse which they call a wah, and which is approximately a pouce less than our toise; it doesn't take much for their 8 grains of rice, which is their “finger”, to equal 9 of our lignes which we estimate as equal to 9 grains of barley.

[Simon] de La Loubère.
Du Royaume de Siam. Tome Second.
Amsterdam: Abraham Wolfgang, 1691.
Page 48.