Been to Maesai<>Tachilek today for another 90-day stamp on my non-B. This time they took pictures of my passport and Visa, as well the arrival card and they asked me to repeat my address from the top of my head. Then got stamped in without any further hassle.
Dunno for what reason this all was. But I think there's something brewing again for sure. Just to let all you people know.