Water morning glory (pak bung — Ipomoea aquatica) stir-fried at extreme heat with garlic, fresh chillies, yellow bean sauce (tao jiew), oyster sauce, and fish sauce — one of the most dramatic wok preparations in the Thai street food canon and one of the few in which the vegetable's quality is the primary variable. Morning glory's hollow stems and tender leaves wilt rapidly and completely in 2 minutes of extreme wok heat — but they wilt to a bright, vivid green rather than a collapsed grey-green because the extreme heat instantly evaporates the surface moisture and begins the Maillard process on the outer surface before the interior moisture can steam the vegetable.
**Morning glory preparation:** Cut into 8–10cm sections, including both stems and leaves. The stems require slightly longer heat exposure than the leaves — they are added first or the wok heat must be extreme enough to cook both simultaneously (the street vendor's approach). **The flung wok technique (the dramatic element):** Thai street vendors making pak bung fai daeng (literally 'morning glory on red fire') fling the dressed wok across the open flame above the wok burner — the morning glory arcs through the flame, receives a brief direct contact with the fire, and develops a slight char and a smoke note from the direct flame exposure. This is wok hei at its most visible (Entry TH-49). It is not necessary for the home cook — but the principle of extreme heat and deliberate flame contact is the goal. **The yellow bean sauce (tao jiew):** Fermented yellow soybean paste — similar in principle to miso but with a different flavour profile. Salty, earthy, slightly sweet. Combined with oyster sauce: a complex, layered savouriness that carries the morning glory's clean, slightly vegetal flavour. Decisive moment: The wok temperature at the moment of the morning glory's addition. The vegetable wilts and cooks in 2 minutes. In those 2 minutes, the wok must maintain maximum temperature throughout — because the morning glory's high water content continuously cools the wok. The cook must keep the heat at maximum and toss continuously to ensure every portion of the morning glory contacts the wok surface in sequence.
David Thompson, *Thai Food* (2002); *Thai Street Food* (2010)