Transpac, as the author of the blog, I can tell you that the photos are real, I took them this week. I have spent 9 months over the last two years working in Bangkok and have been traveling there for the past 5 years. It's gotten worse every year and seasonally it can be quite bad especially at rush hour. The rain helps clear it out, but if you're there in dry season it's much more noticeable.

I wouldn't not go to Bangkok because of the smog, but I also would spend more time in other areas of Thailand especially if a traveler has asthma or other health issues.