Prosecutors tell TMZ ... the "Jackass" star appeared in a Chester County court on Monday, where he faced the music over an alleged probation violation. We're told his wife, Dannii Marie, was in the the courtroom ... though, no other family members were present.

Bam's lawyer Michael T. Van Der Veen tells us Margera is still incarcerated following his arrest and has been ordered to receive an addiction evaluation tomorrow before returning to the Justice Center Wednesday for a follow-up hearing.

We're told the reality TV personality is expected to be released tomorrow or Wednesday at the latest.

Van Der Veen continued ... "Bam has been doing very well and for the past year or more has passed all his drug and alcohol screenings. His professional life has been going well and we look forward to his release so he can continue his growth."

As we previously reported, Margera was sentenced to 6 months probation back in June ... after pleading guilty to 2 counts of disorderly conduct. He had previously been charged in relation to an incident from 2023 after being accused of assaulting his brother and threatening his family before fleeing from the police.

Margera eventually surrendered himself to the authorities ... where he negotiated a plea deal.

Margera has stayed out of trouble for the most part since then ... that is until he was arrested on Sept. 16 and charged with driving under the influence of alcohol or a controlled substance, summary reckless driving, and other related charges.