Complex sentence: The majority of people in present-day Isan are Lao-speaking; many Khmer-speakers live in the southern part; and substantial minorities of Katuic (i.e. Kuy, Bru, and So) speakers also exist.
Split into simpler sentences: The majority of people in present-day Isan are Lao speaking. Many Khmer speakers live in the southern half, and substantial minorities of Katuic (i.e., Kuy, Bru, and So) speakers also exist.