The death of L.B. Bonner -- who was featured on the show "My 600-lb Life" -- has officially been ruled a suicide ... according to the coroner's report.
As we reported ... Bonner was found dead last week in park in Lexington, South Carolina with a gunshot wound. According to the County Coroner's Office ... he died from a self-inflicted single gunshot would to the head.
Before his death, L.B. posted a cryptic message on Facebook saying, "I just want to say thank you to everyone who has shown me love and support throughout my journey...I've realized a few things over the last few days and its time that, I face my demons head on."
Bonner appeared in last season's '600-lb Life' ... which documented his journey as he went from 642 pounds all the way down to 316.
He was 30.