Smoking is a person's choice of living. Smoking in his house is also his choice, he has no control of the air flow though. So if the smoke gets into our homes, the only thing to do is talk to the smoker below. If not then I think you have to live with it.
Living in HDB flats, the thing we have to adapt to is tolerance. Not just to smokers but also to bad karaoke singers, noisy neighbours, furniture dragging etc...
So while you engage in the normal habits/ECAs you normally do, think of those who don't...