In 2018, Bangkok averaged 27 micrograms of PM2.5. That puts Bangkok just under three times the WHO annual limit. In the summer, air mixes to higher up in the atmosphere, so pollution is less concentrated. But in the winter, the air stays closer to the earth, so we stew in our own waste. In Thailand, the winter also brings smoke from crop burning.
Click here to read more analysis details: https://smartairfilters.com/en/blog/does-the-climate-in-bangkok-aggravate-the-air-pollution-in-the-city/