Thai policemen - always on duty or not ?

[arsenal]

All groups of tourists are horrible, all of the time and in all places.

And Latin. A brief look at the history of WW II might re-evaluate your opinion. Assuming you can read. Britain won the Battle of Britain before Pearl Harbour took place.

Getting back to the original topic. I suspect that all Thai policemen are considered on duty if they're in uniform. The easy way to tell is if they're wearing guns. A gun signifies they're real police and not the plastic ones we see (usually blowing a whistle) out and about sometimes.