Judge Mark Young said Thursday he was concerned the actress had completed fewer than 10 hours of service over three years.
Lohan is on probation for a 2012 reckless driving case filed after she crashed her sports car in Santa Monica on her way to a film shoot.
Lohan's lawyer Shawn Holley says the "Mean Girls" star will move from London to complete about 115 remaining hours of service working with kids in New York.
Santa Monica city prosecutor Melanie Skehar was skeptical Lohan could pull off the feat by May 28.
Skehar says her office will be seeking jail time if Lohan fails.
Lohan was not required to attend Thursday's hearing.