If serving rice in fresh pineapple, halve the pineapple lengthwise, leaving the leafy top intact and cutting through it. Hollow out each half, reserving 1 cup of the fruit for the rice and extra for garnishing. Save remaining pineapple for another use. Make a small slice on the outside of each half to create a flat base to hold the pineapple steady. Set aside.

Crumble the cold rice between your fingers to separate the grains, and set aside.

Heat 2 tablespoons of the oil in a wok or large skillet, swirling to coat the pan. Add the onion and toss until soft, 3 to 5 minutes. Add the garlic and toss until fragrant and soft, about 1 to 2 minutes. Add the ginger and toss for another minute.

Add the remaining tablespoon of oil, then add the rice. Fry for 2 to 3 minutes over high heat, then add the beans, tomatoes, and pineapple, and fry 2 to 3 minutes more. Add the fish sauce and sugar, and toss until ingredients are well combined and rice is heated thoroughly, about 5 minutes. Add the green onions and toss to combine. Remove from the heat and transfer to a serving platter, or if using fresh pineapple, fill each half of prepared pineapple with warm rice and garnish with extra chunks of pineapple.