Most sites such as airvisual.com & aqicn.org show AQI on the map, not pm2.5 concentration. Different things. Can calculate AQI from concentration here https://airnow.gov/index.cfm?action=airnow.calculator
pm2.5 concentration of 59 = AQI 153. If you have your own pm2.5 meter, you can convert to AQI.
A "safe" AQI of 50 = pm2.5 concentration of 12ug/m3! Rarely seen in Chiang Mai!