Place the olive oil in a wok or large cast iron skillet and place over high heat. Add the onions and cooking until softened and lightly golden around the edges, about 5 minutes, stirring every couple minutes. Add the garlic and cook for a minute more.
In a small bowl, whisk together the soy sauce, oyster sauce, and Thai fish sauce until combined. Set side.
Add the summer squash, half of the tomatoes, and half the soy sauce mixture and stir to combine. Allow to cook until the tomatoes have softened significantly and released a lot of their moisture, about 7 minutes, stirring every couple minutes.
Add the rice, the sliced chili, and the remaining soy sauce mixture and stir to combine. Cook until there is no longer any liquid in the bottom of the pan and the rice on the bottom of the pan starts to get crispy, about 5 to 7 minutes more.
Remove from heat, toss with the fresh basil leaves and the remaining fresh tomato slices, and serve.