Background: Posttraumatic Stress Disorder (PTSD) is a psychiatric disorder found in individuals afflicted by a traumatic event including the natural disaster. "Tsunami" occurred in Andaman coast of Thailand on December 26, 2004, in which 33.6% of survivors were diagnosed as PTSD. This study aimed to explore the single nucleotide polymorphism (SNP). rs267943 genotype is located on chromosome 5 in the intron of the death-associated protein 1 (DAP1) gene and psychosocial factors for PTSD. Methods: Participants (N = 1970) were recruited from volunteers who have complete data both of DAP1 gene and psychosocial factor. Results: Using a binary logistic regression model, significant gene-environment interactions were found for the single nucleotide polymorphism (SNP) rs267943 and psychosocial factors including depression (adj. OR = 6.0, 95% CI = 4.29-8.39), neurotic personality (adj.