Make the wrappers by whisking together the rice flour, tapioca starch, and salt in a bowl. Pour in the boiling water and sesame oil, stirring quickly with a fork until a dough forms. Once cool enough to handle, knead for about 2 minutes until smooth and pliable. If the dough cracks, add a tiny bit more warm water. Cover with plastic wrap and let it rest for 10 minutes.
In a separate bowl, mix together the cream cheese, crab meat, green onions, garlic, tamari, and sesame oil until well combined and smooth.
Divide the dough into about 20 small balls. On a surface lightly dusted with rice flour, roll each ball into a very thin circle, roughly 3 inches across. Keep the finished wrappers covered with a damp towel so they don't dry out.
Place about 1 teaspoon of filling in the center of each wrapper. Dip your finger in water and moisten the edges. Fold the wrapper in half to form a triangle and press the edges firmly to seal, making sure there are no air pockets.
Heat about 2 inches of vegetable oil in a heavy-bottomed pot to 350 degrees F. Fry the crab rangoon in batches of 4 to 5 for about 2 to 3 minutes, turning once, until golden and crispy on both sides. Transfer to a paper towel-lined plate.
Let them cool for just a minute or two, then serve hot with sweet chili sauce for dipping.