A Lotus for Miss Quon - Lang Jeffries (1967) - So Lau Yuen, Shui Tau Tsuen

Further confirmation of my original guess concerning the whereabouts of the village seen during the film intro comes later in the film as Lang is surreptitiously arranging his exit from Vietnam with the local gangster. He has set up a meeting a the "Buddhist Temple" but has the police on his heels.

The so-called temple turns out to be So Lau Yuen in Shui Tau Tsuen (i.e. the village next to Shui Mei Tsuen), Kam Tin. I have yet to venture out this way for exploration (I did once go to Kat Hing Wai but it was many years ago) but a quick search for the building confirms that it is indeed the same place seen on film.

Edit: I had previously believed only the Yi Tai Study hall was used in this sequence, but it turns out both sites feature. The scenes with the monk were filmed at Yi Tai Study Hall and the outside shots with Lang Jeffries were at So Yau Luen. How confusing!