Bam Margera left detox early and is telling friends he's going to spend the weekend in Las Vegas ... sources familiar with the situation tell TMZ.
The former "Jackass" star had been detoxing in San Diego at a place Lamar Odom helped him get in, but we're told Bam didn't want to complete the program ... and on Monday he bounced.
Our sources say Lamar was desperately trying to get Bam to return to the detox center and finish up at Odom Wellness Treatment Centers, but Bam instead agreed to stay at Lamar's home in Calabasas this week, with Lamar continuing to encourage Bam to finish treatment.
Despite Lamar's best efforts, we're told Bam bolted Thursday ... and he's since been telling friends he's planning a weekend trip to Sin City.
Bam dined at Nobu in Malibu with a friend Thursday ... shortly after leaving Lamar's place ... but it's unclear who is joining him on his Vegas trip.
It's a sharp turn for Bam, who started the detox June 7 after cops put him on a 5150 psychiatric hold following a video rant where Bam threatened to smoke crack until he died or saw his son, Phoenix.
Bam's said his son is his motivation for getting sober, and his estranged wife's recently allowed the two to interact on FaceTime calls ... but now it appears Vegas is calling.