If its for a genuine reason, Ok, if its just cant be arsed then it creates a climate that just makes it difficult for the rest of us who do obey the rules.
And the people who say ignore it are the same people who will end up with lung diseases first and the general decline in health second. There is a huge rise in lung cancer in Thailand. Don't be a statistic.
PM 2.5 at those levels was dangerous. The stuff penetrates every organ of your body, including the brain. The long term damage might take a while to show up, but why risk it. Until Thailand changes, visiting between mid Nov to mid Ap is dangerous.