I googled around on this question but of course there are large differences between different places on Earth.. some places you're not doing a whole lot of agriculture between November and March for example.
So for Thailand, assuming there's plenty water available, how many rai would you need per person to grow pretty much all your food yourself? (So including some chickens/ducks and fish, but not necessarily including larger livestock.) In addition you'd have rice or other grains/corn and/or potatoes, fruit, a vegetable and herb garden, etc.