Isaiah saw the Lord on a high throne in the year which king died?

Answer: Uzziah

"In the year that King Uzziah died, I saw the Lord seated on a throne, high and exalted; and the train of His robe filled the temple."

“In the year that King Uzziah died, I saw the Lord seated on a throne, high and exalted; and the train of His robe filled the temple.”— Isaiah 6:1 (BSB)