The regular smile emoji shows that you care about the topic but, at the same time you don't want to listen to their thoughts on the topic. You only sent that emoji so you do make the other person feel bad about speaking to you.
It can also mean that someone told you a joke and you either felt the following:
The joke was...
-Dumb
-Stupid
-Insulting to you or others
-Lame
-You didn't get the joke
If you felt any of those feelings about that joke, you would have sent the regular smile emoji and not the cry/laughing emoji because you don't want them to feel bad.
