Kudos is Greek for glory, and traditionally singular. 'Kudo' is a back-formation; 'kudos is due' is the safe form.
Kydos was the glory a hero won in battle, often granted by the gods. English took it as a singular word. 'Kudo' is a back-formation: the s was never plural.
Kudos to whoever brought kolaches to the Monday meeting.
Give kudos in Slack by name, for something specific. It's the oldest reward in the book.
Practice it in Skepsis