When you say he is dressed as a clown, you mean he is actually wearing a clown costume. Can you say he is dressed like a clown when you would like to express his clothing somewhat reminds you of clown costumes? Or, do they both mean the same? Could you help me clarify it? Thank you always.
"as" is much stricter than "like"
In the former, yes they are in a clown suit. In the latter there are either similarities (obviously not actually in a clown suit else "as" would be used) or that the speaker wants to express that the person looks comical, silly or just unusual (e.g. pants on backwards, something inside out or socks with sandals).
You could imagine a cartoon of a clown school reunion where one fellow turns up in a suit and tie and one of the others saying "gee Roger, you look like such a clown."