The spring and summer of sequels continue with The Hangover Part II, a follow-up to the record-breaking 2009 hit about a bachelor party in Las Vegas that goes off the deep end.

History repeats itself with The Hangover sequel, in the film’s raunchy storyline and at the box office. Again, Phil, Stu and Alan wake up the morning after with no memory of the previous night’s madness. And repeating the first movie’s box office windfall, the guys’ latest debauched misadventures collected $137.4 million, a record for an R-rated comedy in its first five days.

Returning writer-director Todd Phillips doesn’t mess with his winning formula. There’s a wedding, a bachelor party and a missing person. But the setting moves to Thailand, where Stu is to marry Lauren, a young woman whose youth, beauty and gemlike character suggest she’s way out of his league.

Lauren’s strong-willed dad insists that her wedding be held in his homeland. He’d much prefer that his daughter not marry Stu, a man whose character he likens to watery white rice. Dentists, such as Stu, aren’t even thought to be real doctors in Thailand.

Hangover II’s more amusing scenes include an uncomfortable reunion of Hangover I’s guys gone wild in Vegas. Returning cast members Ed Helms and Bradley Cooper, playing Stu and Phil respectively, visit the still-unhinged Alan, again played by Zach Galifianakis.

Alan follows contemporary film comedy’s habit of rendering men as overgrown boys. Maybe feeling the pressure to top the many man-child movies that preceded it, Hangover II amplifies Alan’s childishness. He identifies himself as a stay-at-home son. His parents treat him like a spoiled 12-year-old. It’s a funny, strange situation that anticipates the grim turns this often dark comedy is about to take.

Galifianakis’ Alan is the capricious force who propels The Hangover series. The actor belongs to the funny-faced, overweight school of gonzo screen comics that claimed John Belushi, John Candy and Chris Farley. Trouble-magnet Alan, however, has a technological advantage over the comic characters Galifianakis’ forebears played: Alan instigates disaster with swift efficiency thanks to that ubiquitous post-20th-century device, the cell phone.

Meanwhile, Stu participates in his own destruction. “All right,” he says. “One drink.” Before you know it, he says, “I can’t believe this is happening again!”

Helms’ Stu and Cooper’s Phil mostly react to the crazy stuff instigated by Alan and Ken Jeong’s gangster and party- starter, Mr. Chow. Stu breaks into nerdy panic and Phil swears. Neither of them entertain much. Fortunately, there’s a nicotine-loving Thai monkey riding shotgun to pull the slack.

There’s some funny business and lots of nasty things in The Hangover II, plus serious action and a principal character who apparently won’t mind that he’ll never again play a J.S. Bach cello suite. But there’s not enough fun here to make this trip worth taking.