what is the diference between ‘such thing’ and ‘such things’
In modern English, “such thing” is almost always a mistake for “such a thing”. It can, however, validly occur in such phrases as “no such thing”, “any such thing” and “some such thing”.
by your saying,‘such question’ is wrong,we should say ‘such a question’?
Except in certain special cases, such as “no/any/some/one such question”, yes.
However, in case you are from India, I am wondering now if “such question”, and indeed “such thing”, is a special feature of Indian English — perhaps a relic of old-fashioned language that has been preserved in India but mostly lost elsewhere.