Ray J is being accused of sexual assault not for grabbing a woman’s ass at a Beverly Hills bar … he allegedly grabbed her boob in front of witnesses.

TMZ broke the story … Ray J was at Side Bar May 30th at the Regent Beverly Wilshire hotel. He got in an altercation at the bar, was thrown out, the cops came and Ray J allegedly went nuts, kicking out a police car window and spitting on an officer. He’s been charged with 4 misdemeanors, including assault and battery and sexual battery.

The sexual battery is curious. The Beverly Hills PD told TMZ the day after the incident … Ray J did not commit a crime when he touched a woman. We were told he touched her butt and cops said it was “incidental.”

But now law enforcement sources say they’ve found “new evidence” … although it’s weird that it’s new. We now know multiple witnesses — staff and patrons — say they saw Ray J grab a woman’s boob in the bar and now cops believe prosecution for sexual battery is appropriate.

One witness says Ray J came into the hotel “wacked out on something” and pushed an 8-year-old in the lobby as he made his way to the bar.

We’re also told both the lobby and the bar are filled with surveillance cameras. We’re told there are so many cameras in the bar everything can be seen — they can even zoom in on a tab.

Ray J’s arraignment is set for Friday. He is not required to be in court.