Complex sentence: The Portuguese established a trading base in the city of Ayutthaya where they intermarried with the Thai and also brought men and women from other Luso-Asian areas in East Asia, South Asia, and Southeast Asia.
Split into simpler sentences: The Portuguese established a trading base in the city of Ayutthaya. Where they intermarried with the Thai and also brought men and women from other Luso-Asian areas in East Asia, South Asia and Southeast Asia.