Add hot water and sugar to a medium bowl or mason jar. Whisk or close lid and shake to combine.
Add lime juice, then taste for sweetness. The flavor should be similar to sweetened lemonade (or limeade). Add a tablespoon more if needed.
Add fish sauce, chili paste, garlic and whisk or close lid and shake to combine. Add the Thai chilies which add more heat.
Serve as a dipping sauce for spring rolls, egg rolls, summer rolls, or with beef, chicken, pork, or seafood.
Notes
This is how I prefer the flavors as directed by ingredient amounts. The flavor of this dipping sauce can be adjusted to suit your taste preference. Add smaller amounts at a time, then taste for flavor and add more if needed. Remember, you can always add more of something, but you can't remove it after it's been added. It's important to taste the nuoc chom as you make it.
Nutrition shown is for total 1 1/2 cups, as serving sizes may be different for each person.
Store in airtight container, refrigerated, for 2 weeks.