1) thank you to is a prepositional phrase, which means "thank you; Due to; Because (meaning is equivalent to because) ". For example:

Thanks to your help, we finished the work in time. Thanks to your help, we finished the work in time.

Thank you. It means "thank you", where thanks is a plural noun and the preposition for refers to the reason, followed by the ing form of a noun, pronoun or verb. For example:

Thank you for your help. Thank you for your help.

Thanks for inviting me. Thank you for your invitation.