In the past 4 decades, the economy in Thailand has changed from a mainly agriculture base to a broader array of manufacturing and services sectors that now account for about 80% of the country's annual expansion of GDP [6]. In 2007, the total workforce in Thailand was estimated to be 35.7 million people (∼56% of the total population). The major employment sectors in the workforce included agriculture (47%), manufacturing (18%), and industrial service (21%). However, only 9.1 million (∼25%) of the total workforce was employed in the formal sector that was covered by the Thai Workmen Compensation Fund (WCF)