Post-Bong Miley Cyrus -- Not Slacking On Set

Miley Cyrus ain't letting no bong video disrupt her career -- in fact, sources tell us she's "working from early morning 'til late at night" to make sure she nails every scene in her new movie. 

Our sources on the set of "So Undercover" say Miley's been taking her leading role extremely seriously -- working overtime with the director "to see where she needs to improve" -- and requesting additional takes until the scenes are perfect.

We're also told Miley is leaning on her mom, Tish Cyrus, who's on set everyday ... and is a producer on the film.

From all accounts ... sounds like the only thing Miley's burning these days is the midnight oil.

Source: TMZ