Complex sentence: Cambodian history presents the reason for the next Thai attack because King Ang Chan refused to give King Maha Chakkraphat a white elephant when he asked for it, it is indicated that King Ang Chan declined any symbol of vassalage to Thailand.
Split into simpler sentences: Cambodian history presents the reason for the next Thai attack. Because King Ang Chan refused to give King Maha Chakkraphat a white elephant when he asked for it, it is indicated that King Ang Chan declined any symbol of vassalage to Thailand.