If my experience is anything to go by, there is a chance that he already knows he is 'different' and it may be that an explanation will help.

Psychologists can sometimes suggest good coping strategies for things AS people find difficult like social situations and relationships and the National Autistic Society or your equivalent can be a good source of support and help.

Even if he chooses to do nothing about your suspicion, you have at least offered the information in the right spirit much as you might if you suspected someone had some other condition.