Looking for information on who or what time in history the phrase "Hail the King" was used, not hail to the king. When this phrase was said it was followed by what sounds like a foot stomping on the floor, almost ceremonially.
The earliest Google Books match for "Hail the King" is from an ode marking the 75th anniversary of the birth of King George II, in The Gentleman's and London Magazine (November 1757). The chorus of the ode runs as follows:
Triumphant strike the loudest string!
Hail the HERO! Hail the KING!
In contrast, the first instance of "Hail to the King" in a Google Books search is from 1849. Still, neither expression is at all common until the middle of the nineteenth century, when "Hail to the King" enjoys an upsurge in usage (six matches from 1850 alone). The most significant instance of "Hail the king" before 1850 is an instance in Edward Bulwer Lytton, The Pilgrim of the Rhine (1834):
"Behold," cried Morven in a loud voice, "behold your king!"
"Hail, all hail the king!" shouted the people; "All hail the chosen of the Stars!"
Th record of usage that the Google Books database presents suggests that the expression "Hail the King!" was never a common English phrase in writing of any kind at least through the first half of the nineteenth century. Note that the famous lines spoken by the witches in Macbeth are somewhat different:
1 Witch. All hail, Macbeth! hail to thee, thane of Glamis!
2 Witch. All hail, Macbeth! hail to thee, thane of Cawdor!
3 Witch. All hail, Macbeth! that shalt be king hereafter.
Here, Witch 1 and Witch 2 are saying "Hail to thee, thane," not "Hail to the thane."