I knew already since I'd seen the video before, described as "transsexual singer on Thailand's Got Talent." But she does have a couple of physical signals, mostly the length and proportions of her arms and shoulders. But I probably wouldn't have noticed that outright if that aspect hadn't been spoiled for me to begin with, and I may have even been so naive as to think that maybe she just had been practicing sounding like a dude before someone spelled it out for me.
For me, it was the hands. That and "The Ladyman Show" on NY public access. (That show is... is... I'd post some if I weren't so sure I'd get into trouble.)