How do I respond to "Hey Bae" to my fwb?

This is the first time he initiated a convo with "Hey Bae". Deep down inside me I feel he's subliminally hinting that he sees me already as his gf. How can i go to replying to the message without making it seems I'm taking his text normal?
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+1 y
We're only seeing each other
How do I respond to "Hey Bae" to my fwb?
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