In a small saucepan or microwave container, combine the rice vinegar, sugar and salt and heat just enough to completely dissolve the sugar. Let cool to room temperature.
In a large bowl, combine the cucumber slices, onion and chile with the vinegar mixture and toss gently. The cucumbers will seem dry, but the salt will draw out moisture from the cucumbers to create more brine.
Cover and refrigerate for at least 30 minutes before serving. The cucumbers can be refrigerated in a sterile container for at least a week. They probably won't last that long!
Very good with grilled foods and along side any Oriental meal. Enjoy!