after searching for vietnamese sandwiches in queens (although i've yet to look in flushing), i've got some news to report.
thai son off of bway, across from the subway station, makes a pretty good one for $3.50. the ingredients are very fresh and very tasty and they make it up for you on the spot. it's a bit too bready, sometimes, but good. (sometimes they tear out the bready center on the roll and sometimes they don't.) not very spicy. they only have one kind on the menu, which is the standard combo of pate, pork and ham. whoever happens to be on the waitstaff makes it up, so there is a bit of variation from day to day, but i've had it three times and it was always very good. as compared to Ba Xuyen in sunset park, i'd say it holds its own, although thai son doesn't have the variety of sandwiches and doesn't do the volume and doesn't have the awesome durian, jackfruit and avocado smoothies. you can get it to go or to eat in. they're very friendly, too.
pho bang and pho bac on bway in the singa's shopping center no longer make vietnamese sandwiches.
little saigon on bway about two blocks below grand makes a sad and not very respectable version. they have about 6 or 7 sandwiches on the menu. i had the classic, but it wasn't worth eating. it came on a not very fresh italian roll, the meats were tasteless, the pickled daikon and carrot were bland and the pate wasn't tasty.
ny market ( the pan asian grocery in the singa parking lot) sells a version in the bakery. but it looked so sad and tasteless and the bread was so uninspiring that i didn't order it.
i've noticed about 7 vietnamese places in flushing: nam san, maple, man o jang, pho, pho bac, pho bang and mekong. i'll start exploring and report back when i'm finished, unless someone else has done the leg work.