Background: Economic crises during the coronavirus disease (COVID-19) pandemic severely impacted mental health outcomes. However, there is limited evidence on this issue in Thailand. We aimed to evaluate the association of economic burden during the first phase of the pandemic and the risk of adverse mental health outcomes in the Thai population.Methods: We recruited 2,303 participants aged 18 years or above with employment/full-time jobs before the national lockdown in April-May 2020. The measures of economic burden were job loss, income loss, and financial problems related to the outbreak. The outcomes included depressive symptoms, anxiety, and perceived stress. The association between economic burden and adverse mental health outcomes was evaluated using multivariable logistic regression models.Results: Individuals who lost their jobs during the COVID-19 pandemic had a higher risk of perceived stress compared to those who maintained their job (adjusted odds ratio [OR], 2.40; 95% confidence interval [CI], 1.28-4.51; p = .006). A higher risk of anxiety was observed in individuals with a monthly income loss of 50% (adjusted OR, 1.42; 95% CI, 1.03-1.99; p = .035; individuals without income loss, reference group) or over. Self-reported financial problems were significantly associated with adverse mental health outcomes (nonexperienced financial problems, reference group): Adjusted ORs of 1.84 (95% CI, 1.34-2.51; p < .001) for depressive symptoms, 2.00 (95% CI, 1.48-2.71; p < .001) for anxiety, and 2.12 (95% CI, 1.51-2.95; p < .001) for perceived stress.Conclusions: Economic burden, especially self-reported financial problems, was associated with adverse mental health outcomes. However, long-term studies are Chidchanok Ruengorn and Surapon Nochaiwong contributed equally to this study.