Does thank you have a hyphen between thank and you?

The saying "thank you" is an expression of gratitude. It can be hyphenated to form a noun or adjective-"thank-you", denoting a message, utterance, note, letter, gift, etc, expressing gratitude.

Source: http://en.wikipedia.org/wiki/Thank_You

So, here's an example: "Thank you for sending me that thank-you card in the mail."