Rinse chiles, remove stems, and roughly chop. Peel the garlic.
Blend chiles, garlic, rice vinegar, water, sugar, and salt until a coarse, spoonable paste forms.
Warm the neutral oil in a saucepan over medium heat.
Scrape in the chile paste and cook, stirring often, until glossy and slightly thickened, 8–10 minutes.
Taste and adjust with a pinch more salt or vinegar if needed. Let cool, then jar and refrigerate.