1. In a 1 1/2- to 2-quart pan over medium heat, stir anchovy paste until warm, about 30 seconds.
2. Add 1 cup water, palm sugar, tamarind concentrate, chilies, and salt. Bring to a boil over high heat. Reduce heat to medium and cook, stirring occasionally, until mixture is reduced to 1 cup, about 20 minutes.
3. Pour through a strainer into a bowl; discard residue. Cover and chill syrup until cool, about 30 minutes.
4. Up to 30 minutes before serving, mix syrup with fruit.