The Workers' Compensation Fund (WCF) represents only a limited fraction of work-related injuries in the Thai workforce. This cross-sectional study examined 258,986 records from the Thai National Injury Surveillance (NIS) system collected during 2001-2004, focusing on 17,538 injuries coded as work-related. NIS records provided information generally not represented in WCF statistics, such as construction and agriculture. The reported mechanisms in 129 work-related fatalities were particularly informative, including electrical current (27%), transport accidents (20%), and falls (15%). Mortality in transport accidents was dramatically higher when seat belts or motorcycle helmets were not used, whether work-related or not. The findings emphasize the need to use multiple sources of information for a complete picture of work-related injuries in Thailand, and possibly in other countries. The mechanisms of fatal injury indicate areas where focused efforts are warranted.