This sort of retrospective diagnosis of some sort of condition ought to remain nothing more than speculation.

Karl XII of Sweden, though not ancient, could be considered autistic. He was celibate and disliked alcohol, and many of his peers noted his lack of emotion and his extreme tolerance to pain.

As a ruler, Karl XII was focused entirely on war, specifically the Great Northern War against Russia. His losses against Russia led to the dismantling of royal autocracy for a parliamentary monarchy. He went into exile in the Ottoman Empire, where, after constant scheming, he was forced to escape to Norway, where he died in battle.

Edit: Fixed some errors on my part.

I don't think you're going to get a historically sound answer to this question. Autism is hard enough to diagnose today when we know what to look out for. It's going to be even harder when the only information we can get access to is speculative at best based on the understanding of even obvious illnesses. We can look at rulers and guess what may have been the underlying cause of decisions and choices, but when it really comes down to it we can't see their responses to people directly (eye contact, emotion, social skills).

Since this sub requires sources and a certain level of certainty with answers you might find people more willing to speculate about this question in another less strict sub.