The singer was suited and booted Wednesday night in a white tux for his first performance since April 2019 ... singing tunes from his catalog of hits during a dazzling night of festivities at the brand-spankin' new upscale resort.

In the clip, he's seen performing with a band and backup singer ... and later taking to the piano -- basically pulling out all the stops for the evening, for which he was paid a hefty $6.1 million ... according to The Sun, anyway.

JT's return to the stage may be an attempt to distance himself from ex Britney Spears' sensationalized claims in her memoir "The Woman In Me" ... saying she had an abortion while they were together, which she said he pushed for at the time.

She also alleged he'd cheated during their relationship, and put on a "blaccent" for Ginuwine ... among lots of other claims.

JT was supported at the event by his wife, Jessica Biel ... who looked incredible in a plunging white flowing gown as they arrived arm-in-arm. They later topped off their evening with an appearance at the resort's LIV nightclub.

The new 150,000-square-foot Sin City resort/casino ... owned by Jeff Soffer ... which boasts a new era of luxury hospitality, clearly went above and beyond ... with even icon Paul Anka taking to the stage and bellying up to a celeb-packed craps table.

Honestly, this is what you call high-rolling -- JT, Tom Brady, Cher and Tyga all crowded around to watch the dice. Sylvester Stallone and Kim Kardashian also popped up at the event -- and, imagine this ... Kim made a low-key entrance!