The study aims to (i) investigate the knowledge and understanding of Coronavirus disease (COVID-19), (ii) examine the ability of self-protection against the pandemic, and (iii) study the practices of seeking medical and healthcare services during the outbreak, focusing on informal labors from five selected districts within Bangkok, Thailand. The 360 participants of this study were queried using expert-validated questionnaires to collect data according to the study framework. One-Way ANOVA was employed for testing hypotheses. The samples with different personal factors had no statistically significant difference in the knowledge and understanding of the COVID-19 pandemic. In contrast, the workers with different academic levels showed a statistically significant difference in the extent of knowledge and understanding on self-protection against COVID-19 outbreak. The workers with different academic levels and occupations were significantly different in the extent of knowledge and understanding on rights to Universal Coverage Scheme. The recommendations were developed in various forms: actionable policy, for example, providing access to information on universal healthcare and ensuring social protection and health security; practical recommendations, such as enhancing information on self-protection against COVID-19 and providing primary healthcare services; and academic suggestions to future research.