Trim and rinse the Water spinach (kangkung); cut into 3–4 inch (7–10 cm) lengths and shake off excess water.
Toast a small piece of Belacan (fermented shrimp paste) in a dry pan over medium heat for 30–60 seconds until fragrant (this mellows its edge). Let cool, then pound in a mortar or blitz in a mini-blender with Red chilies, Bird's eye chilies, Shallots, Garlic, a pinch of Sugar and a little Salt to make a coarse sambal paste.
Heat a wok or large frying pan over high heat and add Neutral oil. When hot, add the sambal paste and stir-fry 30–60 seconds until aromatic and the oil turns reddish.
Add the prepared water spinach to the wok and toss quickly to coat with the paste. If the greens look dry or need help wilting, add a splash of Water (1–2 tablespoons) and continue to stir-fry.
Cook just until the stems are tender-crisp and the leaves are wilted, about 1–2 minutes more. Taste and adjust seasoning with a little more Salt or Sugar if needed.
Transfer to a serving plate and serve immediately while hot—bright, fragrant, and full of savory heat.
