The sign WELCOME has several meanings and interpretations. For example, it also means: “hire” and “invite.”
My recommendation is that you use this sign to mean things like:
“Welcome, come on into my home.”
“I hired him.”
“I invited her.
I recommend that you do NOT use this sign as a response to “Thank you.”
So, what should you do if someone tells you “thank you?”
I recommend that you reply with one of these: