What about the smog season in another places of this country? ..last year Chiang Mai won the world Pollution Gold Cup. 

It's the same straw being burnt in the same way as the farmers do producing the same particles the same carbon release and the same nitrous oxide emissions. Biomass fuels are just as polluting as fossil fuels. Better to use straw as the basis of building blocks so the stored carbon is never released. Thached roofs and straw bales have been used for thousands of years!