What is the differences between thanks and thank's friend?

please tell me the explanation. I feel confused with this matter, my friend told to me that I was wrong if I said @thank's friend..

Thanks = Thank you 
Thank's = Thank is 

's is written to show possession, but in this case it's a shortenage of 'is'.

Possession example:
''Sara's phone is pretty.''

Shortenage example:
''That's Sara's phone.''
 
Hope this helps.