1-I said something so that he would notice me.
2-I said something for him to notice me.

Can’t these sentences have two meanings:
a-The thing I said was of such nature as to make him notice me
b-I just said something (what I said is of not importance) so that he would notice me.
Everybody else was quite and I said something. That made him notice me.

Maybe a comma after “something” would change the meaning from “a” to “b”?

Yes, the sentences can have those two meanings. A comma would not make any difference.

Note the spelling of ‘quiet’.