Abamectin kills mites (8-legged arthropods), but may not kill thrips, which are insects (6-legged arthropods.)

Try to find other orchid growers in your area. There is a good chance these are endemic where you live, and orchid growers know they need to treat periodically. For example, spider mites are not native to the Sonoran Desert, where I live, but they are naturalized here now, and we must always be watching for them, indoors and outdoors.

However, from the pictures, he could have either or both. That's why I suggested 3 in 1. Not that I disagree with you.

I’m only seeing mites (red critters) and their shed skins (white) in the pics.