Yes....You work at small restaurant in Ayutthaya with your father.
Your father and me is a friend, and you are my friend's dauther..
The purposes of your visit Korea is tourist.
Maybe just showing your e-ticket will be OK.
Don't worry too much. You have yuour return flight ricket, and you know your hotel, then everything will be fine.
Just show your your passport, e-ticket, entry reporting card.
If you can not how to fill the entry reporting card, ask supporter at the Seoul Airport. They will help you.