Ban is removal of the individual, ostracim is total avoidance.
if Tawan put sign " entry for vinapu prohibited" I will be banned. If I enter for absence of sign, but nobody would approach, seat beside or talk to me I will be ostracized.
You are choosing your destinations carefully. Sometimes all it takes is walking 2 blocks away from the main drag to be in very different world, even in very prosperous places.
In some places you may be requred to pay fee for the shop up front.
As for camera on, make sure your have explicit "yes" from the boy in question to avoid problems
I must say that during recent trip I had the same impression OP had, number of rats seemed higher than ever. I was passing by nightly by certain pile of garbage on Sala Daeng, just past Senso going to Silom and congregation there was more than impressive.
But like animals so just were carefull not to step on one.