Can it be "thank" instead of "thanks?" What's the difference between two?

Native speaker’s answer
Rebecca
No, it wouldn't sound natural to say "thank" instead of "thanks!" "To thank" in the infinitive verb form means to express appreciation or acknowledgment. "Thanks" is an expression of gratitude or appreciation to someone. Ex: I would like to thank you for inviting us. = polite tone Ex: Thanks for inviting us. = casual tone