I examine slavery laws, as reproduced in the 1805 Three Seals Code, as well as accounts of Europeans, to compare the legal conditions of enslaved people and serfs in early modern Siam. I argue that the Siamese kingdom of Ayutthaya (1350–1767) was a slave society where contractual self-enslavement was a widespread means for serfs to escape required corvée and military service to the state. I also suggest that differentiating indigenous contractual slaves (temporary, collateral, and permanent), who were protected to various degrees by the law, from enslaved foreign war captives, who were potentially outside of any legal framework, invites us to rethink freedom and slavery as a continuum rather than a dichotomy.