Victoria's Secret Model -- I'm a Muay Thai Fighter ... I'll Even Take On Dudes

Here's a Victoria's Secret model with an actual secret -- she's a real deal Muay Thai fighter ... who's so serious about it, she flies out to Thailand to train with the best.

TMZ Sports spoke with smokeshow lingerie model Gracie Carvalho (32-24-34) backstage at the "Victoria's Secret Fashion Show" in NYC ... where she revealed her hardcore training regimen.

"I go hard," Carvalho says ... "I go all the way to Thailand sometimes to train with guys."

By the way, the training is clearly paying off -- not only does she look insane ... but she's pretty damn impressive in the ring.