Complex sentence: Floating market's food has been sold from boats on Thailand's rivers and canals for over two centuries, but since the early 20th century King Rama V's modernizations have caused a shift towards land-based stalls.
Split into simpler sentences: Floating market's food or canal's food has been sold from boats on Thailand's rivers and canals for over two centuries. However, since the early 20th century King Rama V's modernizations have caused a shift towards land-based stalls.