Straight friend wanting me?

So a straight male friend of mine that has always been into girls is looking at me with more then friendly curiousity...this is weird for me since we've been friends for so long. He also makes ual comments making them into kidding remarks like..."wouldn't that be funny if we did this and this together...oh and that hahaha!" I just laugh awkwardly. How should I handle this? Should I just be flattered?