The bottom line is you need to be an expert on short time-frames. Need to know REG-T, TIMS, SPAN, rates, vol, greeks, about outsourced/third-party execution and guaranteed VWAP, Fed policy, reports, earnings and release data, brokerage software, the players involved (FCM-BD-SD), co-location, internals and their use, index make-up/cap weightings/sector mix, pricing synthetics (futures and options), programming, math/statistics (not the easy stuff). Forum members are likely deficient in most or all of these. Without this stuff, you'll need some kind of advantage. Many rely on bankroll, connections, industry experience, or big income/risk tolerance, faking it, or just plain luck.
You could join @wxytrader's study group. Beyond that, never heard of a forum dedicated to scalping. I get the impression there's quite a few scalpers here, though.
Moons ago, ET had a live chatroom feature... There was a regular mix of scalpers and intraday-swingers. And a few regular lurkers who "watched" during rth and even got questions answered! It was a free, casual, and fun trading room. Alas...
Not to take any cheap shots, but did you notice that even now nobody gave you a direct answer to your question (viz. what forum is good for scalping?). They just gave their personal opinions on what scalping is or is not and other nonrelevant info. My advice: don't even bother asking.
Oh, really? Then why don't ya count the number of "out of the box" replies made above and see if they're all that helpful to the OP.