You're right. But, don't think "do" is singular. It's the plural conjugation (e.g. They do; we do). "Does" is the third-person-singular conjugation of "to do" (e.g. He does.)
Do = plural
Does = singular (as in "He does...")
I hope that helps
(Remember, it's most nouns that show their plurals by adding "s"...not verbs. Perhaps that was the confusion.)