Wa (Thai: วา [wāː], also waa or wah, abbreviated ว.) is a unit of length, equal to two metres (2 m) or four sok (ศอก.) Wa as a verb means to outstretch (one's) arms to both sides, which relates to the fathom's distance between the fingertips of a man's outstretched arms. The 1833 Siamese-American Treaty of Amity and Commerce, reads, "[The] Siamese fathom...being computed to contain 78 English or American inches, corresponding to 96 Siamese inches." The length then would have been equivalent to a modern 1.981 metres. Since conversion to the metric system in 1923, the length as derived from the metre is precisely two metres, but the unit is neither part of nor recognized by the modern International metric system (SI).
- Spotlight on Treaty of Amity Archived May 3, 2012, at the Wayback Machine
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- "History of weights and measures in Thailand.htm". Northern Weights and Measures Center (Thailand). April 2004. Retrieved September 26, 2011.
..."Weights and Measures Act, B.E. 2466" [1923 CE]....[superseded by ] "Weights and Measures Act, B.E. 2542"...Government Gazette, Royal Decree Version, Volume 116, Part 29 a, dated 21 April 1999...effective since 18 October 1999
- ประวัติชั่งตวงวัดไทย (in Thai). Northern Weights and Measures Center (Thailand). April 2004. Retrieved September 26, 2011.