SEOUL — He may not look it, in a spiffy double-breasted suit and a coiffure secured with enough hair gel to reflect the ceiling lights, but the 45-year-old music executive confides a secret as he rubs his temples: He’s hung over.

But he doesn’t mind nursing this headache, at well past 2 p.m. on a Thursday in Seoul. Some of his best songwriting ideas come to him, he said, in the malaise that follows a night of hard drinking.

The man doing the creative suffering is Psy, the onetime global internet sensation whose 2012 viral music video and earworm of a song, “Gangnam Style,” became the first-ever YouTube offering to surpass one billion views and had the world galloping along with him.

The outlandish but irresistibly catchy song and accompanying video — which has Psy doing the tune’s signature horseback dance move in and around Gangnam, an upscale Seoul neighborhood — achieved the breakthrough, worldwide success that had mostly eluded Korean pop acts, or K-pop, before then.