Young Thug's Driver Allegedly Assaulted, Threatens to Sue the Rapper

Young Thug allegedly caused his long-time chauffeur to get the crap beaten out of him at a house party, and now the driver's threatening to sue the boss.

Derrick Thrasher says he worked as a personal driver for Young Thug over the past 7-8 years. He claims YT invited him to a party in L.A. back in May, where he got into an argument with another rapper named Lil Duke.

Now, according to Thrasher's lawyers ... the driver took the high road, and left the party to avoid a brawl. However, Thrasher says duty called -- Young Thug needed a ride home, so the driver had to go back to the party ... and that's when he claims he was viciously assaulted and beaten.

In the letter, sent to Young Thug, Thrasher's attorneys -- Paul M. Aloise Jr. and Ryan P. Molaghan -- say their client was held down, punched, kicked and had a liquor bottle smashed over his head. He claims he ended up needing surgery.

The driver is now threatening a lawsuit against Young Thug and Lil Duke's record label, 300 Entertainment, if they can't agree on a settlement.