The first hint is there are lots of little grammar errors in the post. Mainly missing 'a' or 'the'. Nothing bad enough to make it unreadable or give ambiguous meaning, however enough to realise English is probably not the writers first language.

The second hint for me is the sentence structure of the first paragraph. Every sentence only has one fact / idea in it, however a native speaker would be more likely to string those ideas together into fewer sentences.

For me it was his choice of words; he is phrasing all questions using SE Asia vocabulary.