Heat up a skillet over medium heat, then add the olive oil. Add the onion and season with a pinch of salt and pepper. Cook for 10 minutes, until softened.
Add the minced garlic and cook for 1 more minute. Add the green beans and thyme, and season with more salt and pepper. Saute for 15 minutes, until the raw bite has been taken out but they are still crisp and al dente.
Remove the thyme stems before serving, and add the vinegar for a little bit of brightness. Enjoy!