Heat oil in a saucepan over medium heat. Add curry paste and cook, stirring frequently, until paste begins to stick to bottom of saucepan and become fragrant, 2–3 minutes.

Whisk in coconut milk and bring to a simmer. Continue to cook, whisking occasionally, until mixture turns darker in color and is slightly reduced, about 3 minutes. Remove saucepan from heat and whisk in peanut butter, vinegar, fish sauce, and honey.

Season to taste with salt. Let cool to room temperature, then transfer to an airtight portable container and chill.