Trim and discard the eggplant ends, then cut into thick wedges, like steak frites—first cut crosswise into three 3-inch chunks, then halve those lengthwise repeatedly until you have 1-inch-thick wedges.
In a large bowl, combine 1 qt. of the water and the salt and whisk until the salt is dissolved. Add the eggplant, making sure it is submerged, and let sit at room temperature for 1 hour.
Fill a 5-quart or larger Dutch oven with the neutral oil and secure a deep-fry thermometer on the side. Set over medium-high heat and warm the oil to 375° F.
Meanwhile, drain the eggplant and dry very well with paper towels. In a small bowl, combine the remaining 1⁄4 cup water, oyster sauce, fish sauce, and sugar and stir until the sugar is dissolved. Set this sauce aside.
Add the sliced garlic to the oil and fry until crisp and light golden brown, about 30 seconds. Use a spider strainer to transfer them to a paper towel to drain.
Check that the oil in the Dutch oven is still at 375° F. Set up for the second fry by setting a dry wok or large skillet over high heat.
Carefully slide all the eggplant into the oil. Stir until the eggplant has darkened and caramelized at the edges, about 1 minute. Remove the eggplant with the spider strainer and drain well over the Dutch oven, then transfer to the screaming-hot wok.
Immediately add the chopped garlic and most of the chili rings (reserve a few for garnish) to the eggplant in the wok and toss everything to combine. Add the reserved sauce and continue to toss until the sauce thickens to a glaze and the eggplants are browned at the edges, about 1 minute. Add most of the basil leaves and toss until wilted.
Transfer the contents of the wok to a serving platter. Crumble the fried garlic and scatter it over the eggplant with the rest of the basil and chili rings. Serve immediately.