In a large saucepan, heat the oil for the marinade. add the curry paste and cook, stirring, until fragrant, 1-2 minutes. Add the sugar, coconut milk, water, oyster sauce, fish sauce, soy sauce, lemon juice and garlic. Bring to a simmer, stirring to dissolve the sugar. When simmering, combine the cornstarch with 1 tablespoon of water into a paste. Whisk the cornstarch slurry into the sauce and cook until thickened. Remove from the heat and let cool fully.
Coat the steaks in half of the marinade and refrigerate for 4-12 hours. Reserve the remaining marinade as a sauce for serving.
Preheat the oven to 375°F.
Add the rice, coconut milk, water and sugar to a medium saucepan bring to a boil, reduce the heat to low, cover, and cook for 20 to 30 minutes, until the rice is tender. Fold in the coconut flakes.
Heat a grill or large skillet to medium-high. Remove the steaks from the marinade, discarding excess marinade, and grill for 2 to 3 minutes per side to sear.
Transfer to a baking sheet and roast to desired doneness, 8 to 10 minutes (for medium, the internal temperature should be 135°F, 125°F for rare). Rest for 5 minutes before serving.
To make the bok choy, in a small bowl, combine the oyster sauce, fish sauce, soy sauce, sugar, lemon juice, black pepper and garlic. Heat the oil in a large skillet over medium-high heat. When hot, add the bok choy and cook, stirring, until charred and wilted. Add the sauce mixture and toss to coat. Turn off the heat.
To serve, divide the sticky rice between plates. Add a steak, bok choy and reserved red curry sauce on top.