Complex sentence: In 1961 construction was begun on the port of Laem Chabang, due to overcrowding at the river port of Bangkok, and by 1997 Laem Chabang had become the country's busiest seaport.
Split into simpler sentences: In 1961 construction was begun on the port of Laem Chabang, due to overcrowding at Bangkok Port. By 1997 Laem Chabang had become the country's busiest seaport.