hold your breath. are we talking hours on end or ? and whats a low level breath. do you get closer to the pavement with your mouth ? or do you only open your mouth a teeny tiny bit and take a micro breath. :)
that last one probably helps a lot.
get an aircon with a pm 2.5 filter for your room in the condo. wear a n95 mask while out on your bike or a taxi bike. if you drive a car they make a small usb plug in filter you can get. you will notice a huge difference. this pollution is life taking serious. thailand and south east asia is going to explode with cancer over the next 15 years.
every breath you take at street level in bkk is pretty toxic. mix in smog season with that and you are truly breathing poison.