It is curious how one finds the basic sweet and sour dish in the cuisine of every southeast asian country. Filipinos have escabeche; the thai have their pad preow wan wai (they even have a name for their sweet and sour saucenam jim priao wan); the malaysians have a cooking style known as masak blandah/belanda, and theres this vietnamese sweet and sour chicken dish with lemongrass and tamarind. Unlike the basic chinese sweet and sour sauce that is made by combining vinegar and sugar, the sweet and sour sauce of this chicken dish is made by mixing together sugar and tamarind juice. Yes, it is still sweet and sour but the tamarind gives the sauce a fruity and richer flavor that vinegar does not have.