Amanda Bynes was driving aimlessly for hours Tuesday ... while smoking out of what appears to be a marijuana pipe and tooling around L.A. on a suspended license.

The photos -- obtained by TMZ -- show Bynes taking multiple hits out of a pipe that is designed to look like a cigarette lighter in your car.

In one shot, you see what appears to be remnants of marijuana in a cup holder. Some of the nugs appear burnt -- as if they had already been smoked.

The car is a mess. Trash is strewn everywhere. There are stains on the seat, empty bottles, dog hair and various other items.

Amanda started her journey at Baja Fresh in the San Fernando Valley, where she smoked from the pipe in the restaurant parking lot and ate tacos. She then went to a spa, where she spent 3 hours. We're told Amanda then drove without purpose for several hours, sometimes cutting off other drivers and violating various traffic laws. Amanda ended up at Home Depot, where she again took a hit from the pipe in the parking lot.

TMZ has confirmed ... Amanda is driving illegally, because the DMV suspended her license on August 25. As for why her license was yanked, we believe it's because she refused to take a sobriety test when she was busted for DUI in April. In California, such refusal results in automatic license suspension.

TMZ broke the story ... Amanda has been charged with 2 hit-and-runs and various drivers have complained that she has either hit them as well or created peril.