Inside the Xanth series by Piers Anthony, the Naga can be a race of human-headed serpents which can transform in between fully human and serpent forms, which includes any species and size of snake. Phaya Nak or Phaya Nāga (Thai: พญานาค; RTGS: phaya nak; lit. 'lord of Nāga', phaya derived https://mhnaga26.com