The chewy shell is entirely rice flour, but the crunch you taste first comes from a coat of sesame seeds pressed on before it ever hits the oil.
Rice flour dough is wrapped around a sweet mung bean paste filling, rolled in sesame seeds, and deep-fried until the outside turns golden and crackling while the inside stays soft and chewy. Battambang market stalls sell them warm, piled in baskets next to other fried sweets.