3-625: The rai , ngan , and tarang wa or square wa 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). 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 ('work') is equal to 100 square wa , and one rai ('field' or 'plantation') equals 4 ngan or 1 square sen . The units were standardized in square metres when Thailand (then Siam) adopted
6-688: Is discouraged by some government documents. Thai units Thailand adopted the metric system on 17 December 1923. Before metrication , the traditional system of measurement used in Thailand employed anthropic units . Some of these units are still in use, albeit standardised to SI/metric measurements. When the Royal Thai Survey Department began cadastral survey in 1896, Director R. W. Giblin, F.R.G.S. , noted, "It so happens that 40 metres or 4,000 centimetres are equal to one sen ," so all cadastral plans are plotted, drawn, and printed to
9-526: The metric system in 1923, although the Royal Survey Department was already reported in 1908 to be using the metre-based conversion for its cadastral maps . The units are commonly used for cadastre and property matters, and official and legal documents express areas of land in such units. 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
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