Central Thai — morning glory stir-fry is a street food staple across Thailand, but the fai daeng technique is specifically associated with Bangkok Thai-Chinese restaurant wok cooking
Morning glory stir-fry with fire (fai daeng = red fire) refers specifically to the technique of stir-frying water spinach (pak boong, Ipomoea aquatica) in the highest possible wok heat, with yellow bean sauce (tao jiew), oyster sauce, garlic, and bird's eye chilli until the leaves are wilted but the stems retain crunch. The 'red fire' of the technique is the result of the oil catching the wok flame when the vegetables and sauce are tossed — the brief spectacular flare develops the characteristic smoky, slightly charred note that defines this dish. This wok-flame moment is what street cooks perform theatrically at Thai street restaurants.
The tao jiew-oyster sauce seasoning is the distinctly Chinese-Thai element of this dish — the fermented soybean note adds depth that plain fish sauce cannot provide, connecting this preparation to the Bangkok Chinese-Thai culinary lineage.
{"The wok must be at maximum heat before pak boong is added — the flash-fry takes 45–60 seconds total","Tao jiew (yellow bean sauce) and oyster sauce combination is the authentic seasoning","The 'fai daeng' moment: tossing the vegetables allows the oil to briefly contact the flame — this is intentional","Stems go in first, then leaves (10 seconds later) — the stem takes slightly longer to cook","Serve immediately — pak boong continues cooking in residual heat and becomes too soft within 2 minutes"}
For domestic cooks without the jet-burner output required for true fai daeng technique, the closest approximation is a small amount of lard or peanut oil (higher smoke point) and the hottest possible burner setting, with the wok pre-heated for 4–5 minutes before adding any ingredient.
{"Adding water to the wok — eliminates the fire-contact possibility and produces steamed pak boong","Low or medium heat — produces soft, steamed morning glory without the char note","Uniform cooking of stems and leaves — the stems need more time than the tender leaves","Over-seasoning with tao jiew — it is salty; excess makes the dish aggressively saline"}