can the bed in cab be folded?

Some have an upper bunk that can be folded up, and some have a stationary upper bunk.

There is a volvo I think that had a lower bunk that could be folded up into two small benches and a table.

There might be others that can do that.

 

Most trucks have two beds. Over/Under.
the lower berth is there to stay. Most allow you to lift up and there is storage under them.
The upper berth can fold up flat against the back wall.
Neither is in the way when you're driving. They're behind you, just like the back seat of your car.

 

Yes. Sometimes. Maybe.

The first truck had only one bunk. Low roof. Yuck. Had the appeal of a Frat House bean bag chair. Sticky mess.

Now I have two fixed bunks. The A/C unit takes up the whole underside of the lower bunk and most of the space between storage boxes. But, I do not have to idle to use it so it's a keeper.

Each one is different so all that matters is what you are given to drive and how you make it work for you.