I approached it from Th. Samsen, walking east on an unmarked lane toward a supermarket parking lot; the noodle shop is at the intersection with another unmarked lane, which extends from the south side of Th. Nakhon Chai Si and passes the Si Yan Market (shown above). If those monks had a mind for pork and garlic, they'd be on the proper path.
I found my own guidance in the work of Suthon Sukphisit, a food columnist for the Bangkok Post whose articles, sadly, are difficult to track down online. Writing about Big Head Noodles (the name may have described a long-ago proprietor), Sukphisit described how the wheat noodles are dipped in hot water, then cold, then hot again, a traditional Cantonese cooking style that provides a superb chewy consistency. He added that the noodles, roast pork, and pork wontons should be eaten dry (that is, with the soup on the side) to give full play to the crispy fried garlic used as seasoning. Sukphisit's words in mind, I pantomimed for an order of "one like that" (with a contour bottle of Coke, 34 baht all in). To little surprise, there's no English menu, though you might glean additional wisdom from the translated website linked below.
Ba Mee Hua Toe
Not far south of Th. Nakhon Chai Si or far east of Th. Samsen, Bangkok
www.bansansuk.com/restaurant/bameihauto