Excerpt from Ben Slater’s blog – http://www.sporeana.blogspot.sg/.
“One of the first images in Wit’s End AKA The GI Executioner is of an elderly Chinese man lying on his side preparing then smoking an opium pipe. Unfortunately this gentleman isn’t a character we’re going to learn anything about, he appears once more, at the end of the titles (about 70 seconds later) continuing his pursuit of opiated bliss (presumably for real) over the celebratory statement ‘Film shot entirely on location in Singapore’. Aside from some interiors in the now long-gone Cathay Keris studio, this claim is true. Filmed in Singapore at the very end of 1969, Wit’s End was the first American film to be entirely made in the Lion City until Saint Jack almost a decade later. The reason you almost certainly haven’t heard of it is because it fell off the radar until the early 1980s. Exploitation film company Troma, who gleefully acquired cheap movies with some degree of violence, sex and grotesquerie, repackaged Wit’s End as The GI Executioner (a title with no relevance to anything in the picture) and it apparently sold well on VHS (and is still available on DVD).”
Read more here.