The fundamental objective of public procurement is to promote efficiency in the procurement process especially to ensure that the supplier offers the lowest price given the acceptable quality of goods and services through a bidding process. However, the collusion among bidders is still a critical problem of public procurement especially the main form of collusion is bid rigging behavior. In Thailand, the government has enacted “Anti-Collusion Law” since 1999; however, bid rigging behavior is still a pervasive problem in public procurement auctions. ...