The rai,[a] ngan,[b] and tarang wa or square wa[c] are customary Thai units of area, used in the measurement of land. They are defined as exactly 1,600, 400, and 4 square metres, respectively (17,222, 4,306, and 43 sq ft).[1]
The tarang wa (square wa, tarang meaning 'grid') is derived from the area of a square with sides of 1 wa (the Thai fathom). One ngan is equal to 100 square wa, and one rai ('field' or 'plantation') equals 4 ngan or 1 square sen.[1] The units were standardized in square metres when Thailand (then Siam) adopted the metric system in 1923,[2][3] although the Royal Survey Department was already reported in 1908 to be using the metre-based conversion for its cadastral maps.[4]
The units are commonly used for cadastre and property matters, and official and legal documents express areas of land in such units.[5] They are sometimes notated in the abbreviated format rai-ngan-tarang wa, e.g. "4-2-25 rai", which means "4 rai, 2 ngan, and 25 tarang wa", though this is discouraged by some government documents.[6]
| Unit | Derivation | Relative | SI (or other metric) | US or UK customary |
|---|---|---|---|---|
| Tarang wa | Square wa | 4 m2 | 43 sq ft | |
| Ngan | 100 tarang wa | 400 m2 | 4,306 sq ft | |
| Rai | Square sen | 4 ngan or 400 tarang wa | 1,600 m2 (16 ares) | 17,222 sq ft (0.4 acres) |
Notes
[edit]References
[edit]- ^ a b Commercial Directory for Thailand B.E. 2496-97 (1953-54) (in Thai and English). Department of Commercial Intelligence, Ministry of Economic Affairs. 1953. p. 3-11.
- ^ Bureau of Weights and Measures. "ประวัติการชั่งตวงวัดของประเทศไทย". In จรินทร สุทธนารักษ์; สาธิต ชูสุวรรณ (eds.). นานาสาระชั่งตวงวัด (PDF) (in Thai). Central Bureau of Weights and Measures.
- ^ "History of Weights and Measures in Thailand". Northern Weights and Measures Center. 2004. Archived from the original on 22 February 2020.
- ^ Wright, Arnold; Breakspear, Oliver T. (1908). Twentieth century impressions of Siam: its history, people, commerce, industries, and resources, with which is incorporated an abridged edition of Twentieth century impressions of British Malaya. London [etc.] Lloyds Greater Britain Publishing Company, Ltd. p. 126.
- ^ สำนักงานบริหารโครงการพัฒนากรมที่ดิน และเร่งรัดการออกโฉนดที่ดินทั่วประเทศ (September 2011). "คำศัพท์ภาษาอังกฤษด้านการที่ดิน (Terminology of the Department of Lands)" (PDF) (in Thai and English). Department of Lands. Retrieved 7 January 2024.
- ^ "คำสั่งจังหวัดเชียงใหม่ ที่ 1/2528 เรื่อง แก้ไข (เนื้อที่ รูปแผนที่ หรือเนื้อที่และรูปแผนที่) ในโฉนดที่ดิน" (PDF) (in Thai). Department of Interior. 1985. Retrieved 7 January 2024.
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