Just hours after landing in Singapore with a gaggle of his buds ... Travis Kelce was firmly planted in a box suite for Taylor Swift's "Eras" tour show -- dancing his face off to at least one of her biggest hits!!

Check out video shot by a fan inside National Stadium ... as Taylor was belting out "Look What You Made Me Do" onstage -- Kelce was getting after it in his seat.

The Kansas City Chiefs star swayed back and forth as he thrust his arms and hips over and over again ... showing no signs of jet lag, this despite flying from the U.S. to Southeast Asia just hours earlier.

Kelce's pals seemed to be enjoying the concert too ... Ross Travis was sitting right by his side groovin' to the tunes -- while Harry Clark posted a vid of Taylor crooning with the caption, "Go Tay Tay."

Afterward, Kelce was waiting for Swift stageside so he could plant a big ole' congratulatory kiss on the pop star.

It's the second time in the last couple weeks that Kelce has flown across the world to watch his girlfriend perform ... in late February, he jetted to Sydney to support her down under.

It's unclear how long Kelce will be in Singapore to be with Swift -- or if any zoo dates are in the works. But she's slated to perform through Saturday night, and with the Chiefs in the middle of their offseason, it seems like a safe bet he'll be around for the weekend.

The two could spend significantly more time together after that as well ... because following her Singapore shows, she's not slated to return to the stage again 'til May.