A unit of length in Thailand, equal to 1/8 inch or 3.175 millimeters. Pronounced "hoon," the unit seems to be used almost entirely for measuring the size of dice
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}