Lyssa Chapman -- I Was Drugged the Night I Got Arrested!

Baby Lyssa Chapman says she has a good reason for highly-publicized arrest last year -- and she plans on revealing that and more in a new memoir about the family ... TMZ has learned.

Baby Lyssa's arrest was a big deal when it happened last March -- and a big part of a recent episode of "Dog the Bounty Hunter." Sources close to Lyssa tell TMZ in her planned memoir, she'll reveal she was drugged on the night in question.

According to our sources ... Lyssa, who has had substance abuse issues in the past but has clean and sober for years, even visited a doctor in the months after her arrest who deemed she did not have a substance abuse order.

We're told the book -- which is being repped by Martin Literary Management -- will also detail problems with Leland and Duane Lee. According to our sources, they've left the bail bond business and severed ties with the rest of the family ... putting next season of the show in jeopardy.

Our sources say the production company behind the show have even sent the two a letter demanding their return to production or face being kicked off the show for good.