1-"I don't think he is student."
2- "I think he is not a student."
The speaker has the opinion that "he is not a student". But in order to say this in English, we make up the sentence like this ""I don't think he is student."
Because I am not a native speaker, from my logical point of view, both sentences seem to give the same meaning". Either way, the speaker has the same opinion about him, which is "He is not a student".
And what is interesting is that this structure is true for these types of sentences that start with "I think, I suppose, etc". These parts of sentences turn into "I don't think...., I don't suppose ...." to make it negative, whereas the negative situation is actually in the second sentence -not in the first one.
So I wonder why can't we form such sentences like this: "I think he is not a student." Why do we really have to make the first part negative in such sentences, whereas the situation in the second part is actually my opinion.
And I really wonder, what would it sound like if sentences starting with "I think, I suppose, etc" were formed the other way around? Would it be a small mistake or completely unacceptable?