Wow, John, what a hassle for you. I fly to Bangkok regularly from San Francisco and have not experienced what you describe (obviously each departure airport is different). I typically board and am screened in Sacramento, California, but occasionally have to clear security at SFO again. And upon return I must clear security in San Francisco for domestic flights. My point is that I'm sorry to hear of your hassles, and hopeful that it doesn't spread to many other airports.
I typically fly with one or two DSLRs and 5 to 7 lenses, a ball head and tools (allen wrenches), laptop, etc. My camera kit gets hand inspected about one out of six or eight outbound flights. UA hand-inspects (sort of) all carry-on bags departing from BKK.
My MFDB kit fits into the same backpacks that I use for DSLR and I'm comfortable with them as carryon. My laptop goes into a separate bag in my roller bag, but must be removed from the main bag on first and last legs of the Bangkok round-trips because the flight b/n Sacramento and San Francisco is a B120 30 seater turbo-prop. AFDII, P25+ and six lenses from 35mm to 210mm fit fine. Never a problem and never weighed.
BTW: I always mention to the screener that "there is a tripod head for photography in that bag" and they typically nod and smile with disinterest. After starting that I have had no closer inspections. Don't know if it's related. The ball head is in my roll-on bag which goes through first. My camera kit is always last through the x-ray, after laptop and shoes (in case I get hung-up waiting for the guy to flag me through).
Flying is a hassle these days.