Smile, laugh with him, compliment him once in a while, tease him gently, and try to be a little bit physical - hug him enthusiastically when seeing him, or lightly tap his arm whenever you want to make a point in the conversation... that kind of stuff. Basically just make sure you have fun with him and talk to him frequently. You two mostly connect through conversation.
All the above is socially acceptable and won't make you look like a weirdo, but still conveys the message you want. Then, it's up to him to reciprocate. Sooner or later it should be obvious wether or not he's into you. If you're feeling bold you can ask him out, but since you have SA that might not be realistic. :b
Voila, not rocketscience, but I think that's really all that's needed.