Ludacris -- Baby Mama Is Workin' 9 to 5 ... To Get Custody Back!

Ludacris' baby mama is taking drastic measures to regain custody of their 1-year-old daughter ... SHE GOT A JOB!!!

According to our sources, Tamika Fuller took losing custody of daughter Cai to Ludacris very hard ... and is trying to get her life in order to gear up for an appeal of their custody arrangement.

Step one, we're told, is Tamika landed a gig in the hospitality industry ... and she's working nights, 40 hours per week to make enough money to support herself and Cai.

Meanwhile a more immediate court battle is looming. We're told Luda wants to take Cai out of the country on vacation, but Tamika thinks their daughter is too young for that kind of travel.