Angelenos Doug Billings and Tracy Garner are about to get married. Two days before the wedding, the four men in the wedding party - Doug, Doug's two best buddies Phil Wenneck and Stu Price, and Tracy's brother Alan Garner - hop into Tracy's father's beloved Mercedes convertible for a 24-hour stag party to Las Vegas. Phil, a married high school teacher, has the same maturity level as his students when he's with his pals. Stu, a dentist, is worried about everything, especially what his controlling girlfriend Melissa thinks. Because she disapproves of traditional male bonding rituals, Stu has to lie to her about the stag, he telling her that they are going on a wine tasting tour in the Napa Valley. Regardless, he intends on eventually marrying her, against the advice and wishes of his friends. And Alan seems to be unaware of what are considered the social graces of the western world. The morning after their arrival in Las Vegas, they awaken in their hotel suite each with the worst ...

Stu is getting married. Along with Doug, Phil, and his soon-to-be brother-in-law Teddy, he regretfully invites Alan to Thailand for the wedding. After a quiet night on the beach with a beer and toasting marshmallows by the camp fire, Stu, Alan and Phil wake up in a seedy apartment in Bangkok. Doug is back at the resort, but Teddy is missing, there's a monkey with a severed finger, Alan's head is shaved, Stu has a tattoo on his face, and they can't remember any of it. The wolf-pack retrace their steps through strip clubs, tattoo parlors and cocaine-dealing monkeys on the streets of Bangkok as they try and find Teddy before the wedding.