11:06 AM PT -- TMZ has learned an understudy will be performing in Wopat's place in tonight's play.

Tom Wopat, who played Luke Duke on the "Dukes of Hazzard," has been arrested for indecent assault and battery in Massachusetts ... TMZ has learned.

Wopat was in Waltham, Mass starring in a play -- a production of "42nd Street." We're told the alleged victim is a woman connected with the production, and the incident involved Wopat allegedly putting his hands down her pants.

According to law enforcement ... police arrested 65-year-old Wopat Wednesday at 10:53 PM. Police were actively looking for him, and pulled him over in his Ford Bronco. We're told cops found a small baggie of cocaine on him, and he was booked for possession.

The indecent assault and battery is a felony. The coke possession is a misdemeanor. Wopat's being arraigned Thursday.

We've reached out to his rep ... so far, no word back. The play is supposed to open with a Thursday matinee, and according to the box office ... show will go on with Wopat.