In 10-inch skillet, cook oil and bacon over medium heat 5 minutes; add sliced onion. Season with a pinch of salt; cook 5 to 8 minutes or until bacon is crispy and onion is soft and lightly browned. Drain.
Add garlic and red pepper flakes. Cook about 1 minute, stirring occasionally, until garlic is fragrant. Add Swiss chard and chicken broth. Cook 5 to 6 minutes or until Swiss chard is tender and has wilted.
Place tortillas on microwavable plate. Cover with waxed paper, and microwave 45 to 60 seconds or until warm.
Fill each tortilla with Swiss chard and bacon mixture, then top with cheese.