I have no idea what Ran is saying for her first sentence. Something about forgetting that Chen's cute tongue is out?

The second sentence is a standard "I wonder what kind of dream she's having."

Yeah, she's been sticking out her tongue for the first several pages so it seems to make sense. Maybe she's talking about how she just forgets to pull in her tongue and leaves it hanging while she's sleeping, though that is some odd word choice.