Two years after their escapade in Las Vegas, Stu, Phil, Alan, and Doug travel to Thailand for Stu's wedding. A mishap during the pre-wedding brunch leads to a series of chaotic events, including a missing bridegroom, a severed finger, a face tattoo, encounters with mobsters, and a rescue mission. As they race against time to find the groom and piece together the events of the night, they face unexpected challenges and hilarious situations.

When a group of friends travels to Las Vegas for a bachelor party, they wake up the next morning with no memory of the previous night. Along the way, they encounter various comedic and chaotic situations as they try to find the missing groom and piece together what happened.

Two years after the events in Bangkok, Leslie Chow escapes from prison. Meanwhile, Alan's reckless behavior causes the group to attend an intervention. On their way to a rehab facility, they are taken hostage by a mob leader who wants them to find Chow and retrieve stolen gold. The group tracks down Chow in Mexico, but he double-crosses them, leading to a series of events that ultimately involve a rooftop chase in Las Vegas and a deadly showdown with the mob leader. In the end, Chow is freed and the group must confront the consequences of their wild partying lifestyle.