Interesting levels in Bangkok

Hi Kontiddin:
First of all thanks for contributing your data - you are still the only member in your area. Your monthly and quarterly graphs show a clear pattern of 5 weekday peaks and quiet weekends, with Monday August 14 missing. I just looked it up and it was a national holiday for you (Queen Sirikit's birthday). So the peaks must be related to work days somehow, which leads to the question for everyone: why? Your outdoor SBM-20 reacts to Beta, Gamma and X-rays, so what could be causing this? My first guess would have been temperature and Radon emissions from the warming ground, but the weekends are no cooler than weekdays (here is last weeks graph from https://www.wunderground.com for Bangkok airport:

If anything, the weekend was hotter.
I know traffic in the city is very heavy on weekdays and smog used to be a problem in the 90's, but it was cleaned up alot by the 2000s. Is pollution getting bad there again? What else could this be? Could local temperatures (as opposed to airport temperatures) be influenced by traffic?