That's what I was wondering too. "Yeah" would be an appropriate translation of "yes", IMO.
Vil du have en kop kaffe? (Would you like a cup of coffee?)
Ja tak. (Yes, please / Yes, thank you)
"Tak" means thank you, but you can add it after saying "ja" (yes) or "nej" (no) in order to sound polite. "Yes, thank you" is the direct translation of "ja tak", but "yes, please" would also be an acceptable translation.
In danish, there isn't a word like "please."
"Be' om" means "please", but it is very informal, and the language that you would expect from a child.