This study investigates the accumulation of microplastics (MPs) in terrestrial wildlife in western Thailand, both inside and outside protected areas (PAs). A total of 136 individuals from 48 vertebrate species were examined, including snakes (44.12%), birds (11.03%), lizards (5.15%), tadpoles (32.25%), amphibians (5.88%), and mammals (1.47%). A total of 387 MPs were found in 44 species, with an average of 3.25 ± 3.63 MPs per individual or 0.05 ± 0.08 MPs per gram of body weight. The quantities of MPs varied significantly among animal groups, with amphibians showing the highest MP.ind⁻¹ rates and tadpoles the highest MP.g⁻¹ levels. Most MPs were fibers (77%), followed by fragments (22.22%), with minimal presence of film (0.52%) and foam (0.26%). The majority of MPs were confirmed as plastics or natural fibers, with PE, PET, PP, PVDC, and PES being the most common polymer types. MPs were significantly influenced by animal body weight, human settlement activity, and land use types. The study highlights the prevalence of plastic pollution in terrestrial vertebrates within Thai PAs and suggests that snakes, obtained from road kills, could serve as a non-invasive method for monitoring plastic pollution. The findings emphasize the need for standardization of solid waste management at garbage dump sites, especially within PAs, and the importance of conservation education on MP occurrence, sources, and impacts to influence behaviors and attitudes toward plastic waste management. The study underscores the urgent need for further toxicological research to establish plastic pollution standards and to understand the long-term consequences of MP contamination on terrestrial ecosystems.This study investigates the accumulation of microplastics (MPs) in terrestrial wildlife in western Thailand, both inside and outside protected areas (PAs). A total of 136 individuals from 48 vertebrate species were examined, including snakes (44.12%), birds (11.03%), lizards (5.15%), tadpoles (32.25%), amphibians (5.88%), and mammals (1.47%). A total of 387 MPs were found in 44 species, with an average of 3.25 ± 3.63 MPs per individual or 0.05 ± 0.08 MPs per gram of body weight. The quantities of MPs varied significantly among animal groups, with amphibians showing the highest MP.ind⁻¹ rates and tadpoles the highest MP.g⁻¹ levels. Most MPs were fibers (77%), followed by fragments (22.22%), with minimal presence of film (0.52%) and foam (0.26%). The majority of MPs were confirmed as plastics or natural fibers, with PE, PET, PP, PVDC, and PES being the most common polymer types. MPs were significantly influenced by animal body weight, human settlement activity, and land use types. The study highlights the prevalence of plastic pollution in terrestrial vertebrates within Thai PAs and suggests that snakes, obtained from road kills, could serve as a non-invasive method for monitoring plastic pollution. The findings emphasize the need for standardization of solid waste management at garbage dump sites, especially within PAs, and the importance of conservation education on MP occurrence, sources, and impacts to influence behaviors and attitudes toward plastic waste management. The study underscores the urgent need for further toxicological research to establish plastic pollution standards and to understand the long-term consequences of MP contamination on terrestrial ecosystems.