It is claimed in various works (eg by James Allen) thаt the king was BELIEVED to have to go through the same procedure, notably the weighing of the heart, as other people before getting his eternal life. However, I find no images of, or textual references, of a king going through this (and so facing the possibility of being denied eternal life), besides one (reproduced by Budge) that is from c. 100-200 AD in Nubia (Kush), which he suggests is a mechanical copy (except for the king's image) of one from the Book of the Dead. On the other hand, the Instruction of Merikare seems to suggest a fear of some unspecified judgement for bad deeds in the Afterlife. None of the the works that claim that the king did go through the weighing of the heart cite any sources. So I am not asking about theology but about the history of Ancient Egyptian theology and the history of Egyptology.
I'd recommend you take a look at the Pyramid Texts which make up some of the oldest religious writings in the world. These were written for the king to aid his soul in its journey to heaven. Yes the king's soul was subject to judgement in the Hall of Truth by Osiris but the 'Utterances' from the Texts were meant as a 'cheat sheet' to ensure that he arrived safely.
Everything in ancient Egyptian belief was magical and the proper words said in the proper way allowed, in principal, for the achievement of any desire.