Lindsay Lohan - I Worked My Ass Off At The Morgue

Lindsay Lohan didn't want to be a stiff during her first day at the morgue ...so she went in and washed soiled linens, scrubbed toilets and seemed to enjoy her time with the other volunteers ... sources tell TMZ.

We're told LiLo said she felt "terrible" about showing up late and being such a distraction on Thursday, so she went to bed early to avoid a repeat performance.

Lindsay, we're told, didn't act like a spoiled brat. Like so many of her friends, she got down on her hands and knees .... and cleaned floors. She even socialized with some of the other volunteers.