The land system of measurement used in Thailand is anthropic units. All cadastral plans are plotted and printed to a scale of 1:4,000.The square wa, ngan and rai are still used in measurements of land area.
The units are the followings: Wah, Ngan, and Rai.
Conversion between Thai measurements and Metric measurements are:
1 Wah = 2 meters
1 square Wah = 4 square meters
100 square Wah = 400 square meters= 1 Ngan
4 Ngan = 1 Rai = 1,600 square meters
Conversion between Thai measurements, meters and acres are:
1 acre = 4840 square yards
1 acre = 4,046.8561 square meters
1 acre = 2.529285 Rai
hectare = 10,000 square meters = 2.471 acres = 6.25 Rai