1 cup rice wine vinegar
2/3 cup fish sauce (nam pla)
1/3 cup firmly packed dark brown sugar
6 garlic cloves, minced
11/2 teaspoons crushed red pepper flakes, or to taste
Combine vinegar, fish sauce, brown sugar, garlic, and red pepper flakes in a jar with a tight-fitting lid. Shake until sugar is dissolved. Serve at room temperature or chilled. Refrigerate until ready to use.
Note: The sauce can be refrigerated up to 1 week.