Complex sentence: The fighting in Laos was of great concern to the Thai government and feared if Laos would fall to the communists, the "Domino Theory" would place the entire region, including Thailand in jeopardy.
Split into simpler sentences: The fighting in Laos was of great concern to the Thai government. The government feared that should Laos would fall to the communists, the "Domino Theory" would place the entire region, including Thailand, in jeopardy.