It may be a funny question.
I wonder about the word "you" in the expression "Thank you". Is it a pronoun like "her", "him", "us", "them" or is the "you" part of standalone expression like "Regards, etc".
In other words, is "thank you" a seperate expression functioning on its own, like a single word, e.g "goodbye" Or is it only the short form of a longer sentence like "I would like to thank to you?
If it is the short form of "I would like to thank to you", then may be I can also say "Thank her" or "Thank them" when I want to thank to a lady or a group of people in the absense of her or them, such as when she is or they are away at the time I thank to them?