How to tell a girl that you want only to stay as friends?

I laugh to give her an impression that maybe I am bored or un-interested, guess it's doing the opposite. I saw her today, and we talked here and there, then she suggested that I cuddle with her. So I'm like "Heh. Sure?", and she was putting her head on my shoulder. Pretty damn positive she likes me now. Like, super-positive.

I don't understand you, Khoi.

"I don't wanna get too close to her."

Next Day
"lol Khoi, can I cuddle you?"

"Sure."