From the Internet :
"Bettas are one of the most recognized, most colorful, and often most controversial fish in the freshwater hobby. Debates rage about the appropriateness of keeping them in small bowls. To fully understand their needs it is important to become familiar with their native habitat.
Bettas originate in the shallow waters in Thailand (formerly called Siam, hence their name), Indonesia, Malaysia, Vietnam, and parts of China. They proliferate rice paddies, shallow ponds, and even slow moving streams. Although many fish keepers are aware that Bettas come from shallow waters, what is often overlooked is the water temperature.
The home countries of the Betta are tropical, which means the water temperature is quite warm, often into the 80's. Bettas thrive on heat, and will become increasingly listless when the water temperature falls below 75 degrees F. Water temperature is perhaps the biggest argument against keeping a betta in a tiny bowl (which cannot readily be heat controlled)."
Rice paddies are FLOODED fields part of the year. Shallow warm water with live plants is their usual home. Shallow is relative, a foot deep is still shallow. They only live in puddles when the water dries up and then they JUMP to another puddle if theirs gets too shallow or muddy.