Peel or scrape ginger with a paring knife. Using a mandolin, slice ginger as thinly as possible (no thicker than 1/16th inch).
Place 2 small jars in a pot. Fill water to cover jars. Bring it to a boil and allow it to continue boiling for 10 minutes. Turn off heat but leave the jars in the hot water until ready to be used.
Combine rice vinegar, sugar, and kosher salt in a small saucepan over medium heat. Stir until sugar and salt dissolve. Let it come to a boil, and then turn off heat.
Fill a medium size saucepan half full with water. Bring it to a boil. Scald ginger for 20 to 30 seconds. Remove with a metal strainer into sterilized jars.
Pour vinegar mixture to completely cover the ginger. Place the lids on and allow it to cool completely before transferring to the refrigerator.
Pickled ginger may be eaten in 2 to 3 days. Keep refrigerated for 2 to 3 months.