Well, my son does this too. He is almost 5yo and recently diagnosed Aspie. Funny thing is, he is often nervous about big group settings and new situations. However, in familiar situations like his classroom, once he gets comfortable, he is OVERLY touchy-feely with his friends, and will hug/kiss friends without asking all the time. They pull away and he doesn't understand why. He told me he made a special new girl friend at school the other day, and when I asked him if they played together, he said, no, he just hugged and kissed her all day! I just cringed imagining the poor little girl and the possible conversation at her home that night! Cute (a little) at this age, but I know he has to learn other kids may not like it so much. We are trying to explain to him about 'asking' if he can hug/kiss. But the problem is if friends say 'no' he either tries anyway or gets mad that they say 'no'.
I've also told him if he needs a hug, maybe he should go ask his teacher for a hug. 'Teachers are good at giving hugs.'
I actually wonder if he is hugging/kissing to try to make up for some social language skills. He wants to communicate--I want to be your friend, I want to play on your level, I want to connect with you, but socially he struggles with that, and so he resorts to what he knows from family . . . hugging and kissing. I wonder if we will need extra help (OT) to get through the physical/social stuff. Actually, had a note from his teacher yesterday explaining he is annoying friends by intruding their physical space and bumping them when he stims. He doesn't understand why they are annoyed.
How does your son respond to social stories on this topic?