A parent asked how she could tell whether her AS-diagnosed teenaged son was getting enough social contact and whether she should be trying to engineer more social opportunities for him. I responded:
He may need nothing other than what he's got. I didn't. Being at school every day was enough social contact for me, even though I didn't "socialize" in the NT way with the other students there. For many AS/autistic people, just being in the presence of others is as much work as it is for a normally social NT person to host a big party. I never wanted further interaction with classmates outside of class, although there was one person when I was in high school who set out to cultivate my friendship and managed to get me interested in doing things together occasionally. I didn't feel lonely because I spent virtually all my time (outside school hours) with family or alone.
I think if you keep track of what interests your son so you can encourage him to pursue his interests, that should be sufficient. He may find that some of his interests are more fulfilling or that he can "get into" them more deeply if he engages in some form of socializing. For example, many AS/autistic people who are not otherwise social enjoy going to conventions or camps devoted to a subject of particular interest.
In general: I suspect (because your son sounds like me) that the only form of socializing likely to "work" for him is the kind with a strong focus on something of great interest to your son and to all the others involved. A group or even a one-on-one friendship based on nothing but "liking" made no sense to me for most of my life. Common interests were what drew me into relating with other people.