Start by heating vegetable oil in a wok or large skillet over medium-high heat. Once hot, add the diced onions and sliced chilies. Stir-fry them until the onions soften and begin to turn translucent, releasing a fragrant base.

Add the minced garlic and continue cooking for another 1 to 2 minutes until the garlic becomes aromatic but not browned.

Increase the heat to high. Add the ground beef and break it apart using a spatula, mixing it thoroughly with the sautéed aromatics. Cook until the meat is well-browned and no longer pink, letting the flavors meld.

Stir in the fish sauce, oyster sauce, dark soy sauce, and brown sugar. Mix everything together and continue stir-frying for another 1 to 2 minutes, allowing the sauces to coat the meat evenly and form a glossy, flavorful glaze.

Remove the pan from the heat and immediately fold in the Thai basil leaves. Stir gently until the leaves wilt from the residual heat.

Serve the hot, fragrant Thai basil beef over steamed jasmine rice or your preferred base. Enjoy immediately while the aroma is at its peak.