Press tofu for at least 30 minutes between paper towels or clean kitchen towels with something heavy on top to remove excess water, then cut into 1-inch cubes.

In a small bowl, whisk together soy sauce, oyster sauce, sugar, and water until combined.

Heat oil in a wok or large skillet over medium-high heat until shimmering. Add tofu cubes in a single layer and cook for 2-3 minutes per side until golden and crispy on all sides. Remove tofu from skillet and set aside.

Add garlic and Thai chilies to the skillet and stir-fry for 30 seconds until fragrant but not burned.

Add bell pepper and onion to the skillet, stir-frying for 2-3 minutes until slightly tender with a light char on edges.

Return crispy tofu to the skillet along with the prepared sauce. Toss everything together and cook for 1-2 minutes until tofu is well-coated and sauce has thickened slightly.

Turn off heat completely and add holy basil leaves, tossing until just wilted from residual heat.

Serve immediately over steamed jasmine rice with a fried egg on top if desired.