Complex sentence: King Rama VII stayed at the palace for a few nights before his coronation in 1925, while King Ananda Mahidol (Rama VIII) made the palace his main place of residence upon his return to Thailand from Switzerland in December 1945.
Split into simpler sentences: King Rama VII stayed at the palace for a few nights before his coronation in 1925. While King Ananda Mahidol (Rama VIII) made the palace his main place of residence upon his return to Thailand from Switzerland in December 1945.