In Sumatra, a meal with fewer than two sambals is unthinkable. The most common is Sambal Oelek, and all you have to do is grind your boiled chilies in a mortar with salt and sugar.
This version omits the vinegar, so it’s less acrid than store-bought versions.
1 cup fresh Thai chilies
1 tsp salt
1 Tbsp palm sugar or brown sugar
Remove stems from chilies.
Boil them in salted boiling water for 5 minutes.
Drain and grind to a purée in a mortar with the sugar and salt.
This sambal keeps for two weeks in the fridge and freezes well.