Fill 1 (14-oz.) glass jar with red and green Thai chile peppers, filling to about 1 inch from top of jar. Bring vinegar, salt, and sugar to a boil in a small saucepan over medium heat, stirring until salt and sugar are dissolved (about 2 to 3 minutes). Remove from heat, and let stand 5 minutes. Pour hot mixture over peppers in jar. Cover and chill 3 weeks. Store in refrigerator up to 6 months.
Note: Chilling for 3 weeks allows the peppers to fire up the vinegar mixture. The longer it sits, the spicier it becomes. Remember to wear rubber gloves when filling the jars with peppers.