Two years after the events in Las Vegas, Stu Price travels to Thailand for his upcoming wedding to Lauren, his fiancée, along with his three best friends Doug Billings, Phil Wenneck, and Alan Garner. Much to Alan’s dismay, they are joined by Lauren’s younger brother, a Stanford University scholar named Teddy. At the rehearsal dinner, Lauren’s father reveals his disapproval of Stu during a toast. Later that night, Stu hesitantly joins Phil, Doug, Alan and Teddy for a beer. Sitting at a campfire and roasting marshmallows, the group toast to Stu and Lauren’s future happiness.
The following morning, Phil, Stu and Alan awaken in a filthy hotel room in Bangkok. Stu has a face tattoo (a replica of Mike Tyson’s) and Alan’s head is completely shaved. They meet a chain-smoking capuchin monkey and discover that their old friend, Chinese gangster Leslie Chow, followed them to Thailand on Alan’s invitation. They cannot find Teddy, and discover only his severed finger. Chow begins to relay the events of the prior night, but he seemingly dies after snorting a line of cocaine. Panicked, the trio disposes of Chow’s body in the hotel’s ice box.
Through a tip from Doug (who is still at the resort as he left the campfire earlier than the others), they go to a police station to pick up Teddy but are given a wheelchair containing an elderly Buddhist monk. He refuses to reveal anything, having taken a vow of silence. After finding a business card, they travel to the smoldering ruins of the business.