The Hangover crew heads to Thailand for Stu's wedding. After the disaster of a bachelor party in Las Vegas last year, Stu is playing it safe with a mellow pre-wedding brunch. However, nothing goes as planned and Bangkok is the perfect setting for another adventure with the rowdy group.

Gentle giant Barney Emerald is drugged and robbed while on holiday in Pattaya. He befriends two Thai siblings, one of which is a muay-thai kick-boxing champion, and stays with them until he can recover his passport. Unfortunately the hunt for his passport makes him cross ways with international gangsters. But Barney has found a secret weapon, the very spicy Thai salad Somtum.

After losing his job, his car and his money, Phuchit, races against time to complete 13 tasks ordered by an anonymous caller who promised 100 million Baht upon completion.