Is holy basil the same as Thai basil?
No. Holy basil is Ocimum tenuiflorum; Thai basil is a cultivar group of sweet basil, Ocimum basilicum, with different chemistry.
The short answer
Holy basil, or tulsi, has slightly hairy, peppery leaves and an essential oil dominated by eugenol, while Thai basil belongs to Ocimum basilicum and carries the anise-like methyl chavicol and linalool profile of sweet basil. In Thai cooking, holy basil is kaphrao (pad kaphrao) and Thai basil is horapha; recipes and health information are not interchangeable between them. African clove basil, Ocimum gratissimum, is a third species sometimes sold as tulsi.