'The Hangover Part II' on the cover of this week's EW

Having delivered the craziest morning-after in cinematic history with 2009’s The Hangover, the team behind the Hangover Part II knew they needed to up the ante for the sequel. But how do you top the mayhem of a rampaging Mike Tyson, a live tiger, Tasers, roofies, and general Las Vegas debauchery? Apparently you go to Bangkok.

In this week’s cover story, Wolfpack members Zach Galifianakis, Bradley Cooper, and Ed Helms and director Todd Phillips gather for a raucous roundtable to talk about how they raised the insanity quotient in the highly anticipated sequel (out May 26). It all started with a script so wild and raunchy — complete with international crime, sexual depravity, a severed finger, and a drug-dealing monkey — that Galifianakis says even he was shocked the first time he read it: “I remember thumbing through it, going, ‘Oh God. Oh God.'”

Shooting the film in chaotic, sweltering Bangkok was a brutal misadventure in itself. “It was the hardest shoot I’ve ever done for sure,” says Cooper. “Nothing ever even came close to it.” Among other things, nearly everyone on the cast and crew was felled at some point by food-related illness–none worse than Helms. “It does something to your mind when you get that sick,” Helms says. “You go to a scared, dark place.” Meanwhile, hanging over the Hangover team was the pressure of trying to live up to the highest-grossing R-rated comedy of all time — a task Galifianakis says he found especially daunting. “I was a little bit apprehensive. I was just of the mindset: ‘Oh, let’s leave well enough alone.’ “

But in the end, the experience had more than its share of high points–including a dinner with Bill Clinton, who was in Bangkok to give a speech and turned out to be a fan not only of The Hangover but all sorts of movies. “The first thing he said when he sat down was, ‘Is there going to be an A-Team 2–and can I be in it?’ ” Cooper says laughing. “I was like, ‘This is a joke, right?'”

For more on The Hangover Part II, including the controversial smoking monkey, pick up the new issue of Entertainment Weekly, on stands May 13. And you can check out EW’s Facebook page and “like” us (if you haven’t already) for access to exclusive video with Bradley Cooper, Zach Galifianakis, and Ed Helms in which they talk about the moment when they knew that the buzz from the original Hangover wasn’t going away, and how they’re currently handling the pressures of success.