Why does Elvis Presley laugh hysterically in his later music.?

I thought this would be a good question to think over. In some of Elvis Presley later songs, you would hear him laughing in the soundtrack for no apparent reason or you would see a recording of him on stage laughing for no apparent reason. I used to hear a few of these songs on the internet and radio, so they are out there. Do they play them on satellite radio also? It would be a lot more fun to hear these silly tracks. Do you think he is just high on something or just having a good time and laughing since he's song all these songs for all these years and just felt like joking around? It isn't done to often nowadays or I have not heard any other singers laughing on a soundtrack for no apparent reason.