In a pot, combine the drained rice, salt, and lukewarm water. Stir, bring to a boil over medium heat, stirring occasionally. Once boiling, reduce the heat to low, cover, and cook for about 10 minutes. Turn off the heat and let the rice sit, covered, for another 12 minutes.
In a small pot, heat the rice vinegar, sugar, and salt over medium heat until fully dissolved. Remove from heat and set aside. Once the rice is ready, uncover it, pour the vinegar mixture over, and mix well.
Line an 8x8 inch (20x20 cm) rectangular dish with plastic wrap, add the sticky rice, and press it firmly into an even layer. Cover with more plastic wrap and refrigerate for several hours, preferably overnight.
After chilling, remove the rice from the plastic wrap. Using a wet knife, trim the edges and cut the rice into equal 1.5x2.5 inch (4x6 cm) rectangles, wetting the knife between cuts.
Heat a pan with oil and fry the rice rectangles until golden on all sides (at 175°C/350°F). Let them cool on a rack.
Combine all the tuna tartare ingredients in a bowl and mix well. Place the sliced avocado on top of each crispy rice piece. Drizzle with olive oil, sprinkle with sea salt, and top each with a spoonful of tuna tartare. Garnish with a drop of sriracha mayo, chives, and a slice of red chili pepper.