One of the few creative jokes in The Hangover Part II occurs when our heroes try to use meditation to access memories of the wild night they had and forgot in Bangkok. Stu (Ed Helms) and Phil (Bradley Cooper) get nothing, but Alan (Zach Galifianakis), whose mind is clearly more open to the currents of universal consciousness, sees a partial montage of the blacked-out events. The joke is that, in his memories, he and his two thirtysomething friends are played by 12-year-olds.

It’s a good joke because it comes out of left field, it’s not explained, and it’s in character — of course paunchy, bearded Alan, who proudly calls himself a “stay-at-home son,” sees himself as a preteen. To him, a drug-fueled evening of riots and hookers is just an especially awesome adventure.

That’s a funny idea for a movie, but its payoff was funnier two years ago, when it was called The Hangover. Returning director/cowriter Todd Phillips has upped the ante by setting the action in a city even more notorious for hedonism than Vegas, but he hasn’t made the premise of men waking up and realizing they’ve behaved badly any more outrageous. Indeed, almost everything that follows from it is so predictable that the humor feels tamer this time around.

Helms’ nebbishy Stu, who ditched his shrewish girlfriend in the last movie, is the one getting married this time — not to Heather Graham’s spacy stripper, unfortunately, but to an inhumanly pretty, patient and tolerant creature (Jamie Chung). Her only drawbacks are her dragonish dad and her coddled, overachieving brother (Mason Lee), with whom our heroes are saddled on their flight to the nuptials at a Thai resort.

This time, there’s no bachelor party — just a beach cookout that somehow ends with Phil, Stu and Alan waking in a Bangkok hotel room to find that certain things have mysteriously disappeared (the brother) and others have appeared (a tattoo, a monkey and Ken Jeong as Mr. Chow, the shrieking mobster from the first film).

Phillips seems to have made a list of everything audiences liked in the first movie so he could give them more of it. Animal reaction shots? Check. Jeong acting seriously wired? Check. Helms expressing mortification in ever more manic ways? That, too.

Most of all, the filmmakers give us more of breakout star Galifianakis, who’s introduced with so much hoopla that you’d think Alan had already become a beloved movie icon on the order of Jack Sparrow. It’s like making Sancho Panza the star of Don Quixote, though: Galifianakis is funniest when he takes us by surprise. Though he gets in a few choice lines here, Alan is fast turning from character to caricature. Cooper might as well not be in the movie, and the same goes for Paul Giamatti, who has a thankless and dispensable supporting role.

The first Hangover was no masterpiece, but it was consistently funny and intermittently shocking — no small achievement. How would you really up the ante on the story of a mild-mannered, politically correct American male (Helms’ Stu, the true protagonist of both movies) who wakes to find he has cut a swath of mayhem through a city that’s no stranger to it? Phillips and co. could have taken their sequel deep into the realms of absurdity and antisocial behavior, but that wouldn’t have sold as many tickets. So we’re left with a rehash of The Hangover’s best moments that feels like a comedy hangover.