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1:02 PM PT -- Ty's agent, Happy Walters, tells us Ty asked for and received permission from the team to miss the flight.

Sacramento Kings star Ty Lawson was partying his face off with teammates at a Vegas club Thursday night before missing a team flight on Friday morning ... TMZ Sports has learned.

Lawson hit up Drai's nightclub along with Ben McLemore and Willie Cauley-Stein and boxer Adrien Broner ... and you can see in the video, they seemed to be having a great time.

Problem is ... Lawson missed the team flight to Kentucky for an exhibition game the next day and Kings' honchos are reportedly demanding an explanation.

For the record, Ben and Willie made the trip and had decent games.

The Kings had said Lawson missed the game due to "personal reasons" -- unclear if the clubbing counts.

According to ESPN's Marc Stein, Lawson also missed a team shootaround in Vegas earlier in the week.