This study assessed the relationship between PM2.5 concentration and the working memory of sugarcane farmers (n = 444) in Khon Kaen Province, one of the largest sugarcane producers in the Northeast region of Thailand. The relationship between the ambient PM2.5 concentrations and the working memory of sugarcane farmers was evaluated using two working memory outcomes. These outcomes included a working memory difficulty score derived from self-report of difficulty in daily tasks that require working memory and an objective memory test score consisting of a set of number recall exercises. The PM2.5 concentration data in this study were obtained from air quality monitoring stations located in the vicinity of the study locations, ensuring both precision and relevance to local air conditions. The regression results showed that farmers in the low-burn farming zone had less difficulty with working memory and better performance on number recall exercises, compared to farmers in the high-burn farming zones, even after controlling for health and socio-economic factors. Our findings highlight the potential impacts of PM2.5 exposure on the cognitive functions of farmers who burn sugarcane residues in Thailand. Our study supports the need for the government of Thailand or health agencies to establish an effective policy to reduce sugarcane residue burning in Thailand.