Just curious, if the phrase "that's" is a shortened version of "that is", would it be okay to say "this's" to shortening "this is"?

Native speaker’s answer
Rebecca
No, this does not happen because of the "s" at the end of "this". It would sound a bit awkward and clumsy if you did shorten it without the "i". One needs to pronounce the "is" part otherwise, it would just sound like "this-s", with a longer "s" sound! If you say it out loud, there has to be a sound of the "i" of "is" to distinguish the two words. Even if you say it fast, there's still a slight difference. Whereas with "that's", the "s" fits in nicely at the end since there is no "s" there already. It's easy to pronounce as "that's"! Ex: This is such a lovely house. Ex: That's my mother over there! Say hi.