Air pollution, particularly fine particulate matter (PM2.5), is a significant health hazard, particularly for urban natives and teenagers. The purpose of this study was to assess the relationship between daily PM2.5 exposure and respiratory symptoms in 132 high school students in Nonthaburi Province, Thailand. From January to February 2025, Daily PM2.5 and students' self-reported respiratory symptom questionnaires obtained online. Results showed a clear relationship between elevated PM2.5 stages and worse respiratory symptoms. The mean PM2.5 concentration during the course of study was 36.2 µg/m³, significantly higher than the recommended safe exposure limit of the World Health Organization. In particular, symptom prevalence increased by 27.6% on days with PM2.5 was exceeding 40 µg/m³ compared to days ≤25 µg/m³. The logistic regression model indicated that PM2.5 concentration was related to 52% higher risk of the occurrence of respiratory symptoms (OR=1.52, 95% CI: 1.26–1.79, p<0.001). The results highlight the urgent requirement for instant air pollution controlling policies, such as school-based monitoring systems, public health education and active intervention to safeguard the development of adolescents in high polluted metropolis.