Miley Cyrus -- Mexican Flag Ass Stunt Triggers Criminal Investigation

Miley Cyrus could go to jail for getting her ass whipped on stage ... with a Mexican flag.

Miley was performing Tuesday night -- on Mexican Independence Day, mind you -- in Monterrey, Mexico when one of her dancers slapped her prosthetic butt with a Mexican flag.

Apparently Mexican officials are super sensitive about disrespecting national symbols so the congress of the state of Nuevo Leon wants her prosecuted. The crime of desecration carries a $1,200 fine and a 36 hour jail sentence.

It wouldn't be the first time a singer crossed the line South of the border. Paulina Rubio was fined $4K for appearing naked in a mag ... draped in a Mexican flag.

Will Miley's butt ever learn?