If you weren't flying F/J and only status pax, then I do have bad news for you: Only priority line for F/J class passengers at BKK nowadays, no more options for high status FF. Even, IF they would hand you a priority pass, you'll have to show the boarding pass and, when not in F/J, your admission to the priority line is denied, despite having such a priority card.

The rude DYKWIA passenger got his/her priority card, but no access to the priority line.

Note: My own experience shows, around 3 of 4 times, the priority card with boarding pass is checked (always on departure, less often at arrival), when entering the priority line.
My impression is, when it's "quiet" and the priority line is not relevant (and sometimes "slower" than the normal queues), there is no checking.

So, the ISM was (probably) right, despite you did not like the message.......