You can write "Come and wish me a happy birthday", "Today is my birthday, thank you for your blessing" and so on. If someone gives you a gift, "Thank you for the gift from XXX, I like it very much". If someone wishes you "Today's birthday, my mother bought me a big cake", "Today someone wishes me a happy birthday first", or simply write "Thank you for your blessing". Signature is to write your own status, such as being in a good mood, or hanging up your favorite sentences, or wishing yourself a happy birthday directly, completely OK. Very casual thing.