Lindsay Lohan -- Better Late Than Never ... Finally On the Job

115 ... 114 ... Lindsay Lohan is finally clicking off her community service hours in a desperate race to keep her ass out of jail -- she reported for work in Brooklyn ... and immediately reconnected with an old, young friend.

Our Lohan sources tell us Lindsay managed to sneak in a back entrance to the children's daycare facility ... dodging all the media gathered out front for her arrival. She showed up about 2 hours after she was expected -- or roughly 90 minutes after most of the kids got there.

Lindsay ran into 5-year-old Donovan who she previously connected with during her docuseries with Oprah Winfrey. NBCNewYork.com tweeted out the photo of the reunion.

We're told she's scheduled to work an 8 hour day (which will leave her at 107 hours to go) -- and administrators will expect her to arrive earlier starting Thursday.