Is it permissible to perform a ruqyah on an autistic son from afar using Quranic verses and prophetic supplications? And what is the alternative if it is not permissible?

A father's prayer for his child's well-being is legislated and, God willing, answered. This is based on the Prophet's (peace be upon him) saying: "Three supplications are answered without a doubt: the supplication of the oppressed, the supplication of the parent, and the supplication of the traveler." A father can pray for his son's protection, well-being, and safety from evil in his absence, based on the Prophet's (peace be upon him) saying: "The supplication of a Muslim for his brother in his absence is answered. At his head there is an appointed angel who, whenever he prays for his brother's well-being, the appointed angel says: 'Amen, and to you likewise.'" We are not aware of any religious impediment to performing Ruqyah for someone in their absence.