Another one with Xiaomi here. Used to use other brands, but one thing that irritated me about those was that they would change the filter design all the time so 6 months after buying the box, and wanted replacement filters they'd say "oh, that's old model, you buy a new box better"... Xiaomi was keeping the same design of filters all up to series 4, so they are easy to get and affordable (at about 800-900 baht for genuine one for series 2/3 or about 1200 baht for series 4, lasting 6-9 months in my case).
The air purifiers are also quite affordable from them, at about 6000 baht for series 4 and about a third less for 3H. All internet connected, so you can control them with phone app and check inside air quality at all times.
In my case (high floor condo, some intentional gaps in window frames for ventilation it seems) the inside air quality is between 5 and 10% of the outside air quality, so 200 outside is between 10-20 inside. They do have displays on so it's easy to see. Right now my outside sensor says 81, with pm2.5 at 26.25 and pm10 at 30.68, AirVisual (same data as aqicn.org/IQAir) ar ground level shows 116, and inside the filters show 6. Fans are silent.
I use Xiaomi 2S (still running after...10? years), 3H and 4. 2S and 3 use same filter type, 4 has a slimmer and taller one.
Coway and LG offer subscription services for 3/5 years, where you pay a monthly service charge to company and they would come to clean and replace filters for you without charge. Both of them look pretty good and easily compete in price with brands other than Xiaomi. I think I saw 490/month (from usual 690/month) from Coway and ~400/month from LG, but it depends on model. Maybe worth considering if you don't want to invest in buying it up-front.
Coway (but you can see their stands at so many shopping malls, which often have better promotions than official site):
https://www.coway.co.th/th/products-list/air-purifier
LG - like Coway, they have physical LG Subscribe store at The Mall Ngamwongwan, Floor 3, the back near exit to parking (and probably elsewhere):
https://lgsubscribethailand.net/
For both of these: at the end of the contract, the product stays with you, but all maintenance and service is included in the monthly price.
And on Xiaomi: They have global and China versions. They share same hardware but Chinese one is all in Chinese, requires Chinese app and loads your data into cloud in China! At least filter cartridges seem not to be region coded and work in any version. Also beware of fake filters - if they write anything about resetting the box manually in change of filter it means filter is fake.