Please help and advise me.
DS 6.3 is a well behaved boy (mostly!), but he seems to have a problem with communicating?
If he's watching TV you have to touch him to get his attention. Sometimes when he's playing and a child talks to him he doesn't respond. If I'm there in the room I'll encourage him/ get his attention. Often I'll say sharply 'DS x is talking to you' and he'll listen but not respond and carry on doing what he's doing.
Now I have got quite annoyed with this in the past but have come to realise he's not being rude he just finds conversation difficult if its not a subject he's interested/ knowledgable in or a child wants him to do something he doesn't want too he'll not answer instead of saying no. He listens to the child and then just stands there until the silence gets too much and then he goes off.
Lately when other children have come to tell tales that DS is ignoring them I have begun to say touch his arm and he'll respond or say its just the way he is/ he finds it hard to talk when he's playing. Sometimes this causes problems as when DS has come out of his world and tries to talk to the children they'll refuse saying they'll ignore him as he ignored them. 
Now I know this sounds precious but I know he's not doing it to be rude.
He can talk for England about something but if you ask him a question he just seems to get confused and wander.
Any advice or help about how to deal with this??