Plastic ingestion by fish species in Thailand represents a significant environmental concern, with widespread occurrence across diverse habitats and potential implications for aquatic ecosystems and human health. This study synthesizes data from 175 assessments encompassing 125 fish species, including marine (77), freshwater (47), and estuarine (1) species, based on a total of 5877 specimens examined. Microplastic ingestion was detected in 84% of species (105 species), with freshwater Cypriniformes exhibiting the highest frequency of occurrence (FO) at 77.75%, particularly among benthopelagic and low-trophic-level herbivorous and detritivorous fish, many of which are commonly targeted in subsistence fisheries. Benthopelagic species exhibited the highest ingestion rates (median = 90.21%), while an inverse relationship between trophic level and microplastic ingestion was observed (linear model: R2 = 0.1775; Spearman’s rank correlation: rs = −0.375, p < 0.0004), indicating a decline in ingestion rates with increasing trophic position. Low-trophic-level species (trophic level 2.0–2.5) exhibited the highest weighted average FO% (67.80%), whereas top predators (trophic level 4.0–4.5) showed the lowest (7.65%), emphasizing the importance of trophic structure in future risk assessments. Detection efficiency varied substantially across analytical methodologies, with chemical digestion achieving significantly higher detection rates (40.27%) compared to visual identification without chemical treatment (6.20%). These findings underscore the need for standardized sampling and detection protocols to enhance accuracy in microplastic ingestion assessments and inform conservation strategies and pollution mitigation policies in Thailand. The study holds critical implications for fisheries managers, conservation authorities, and policymakers, highlighting habitat-specific pollution risks and the necessity of interdisciplinary collaboration to assess potential public health impacts associated with microplastic exposure.