Fire of Conscience. The false donegal clings poorly to Lai's slightly pockmarked cheeks, but the real kicker is the moustache, an unnaturally-shaped sliver of hair spirit-gummed to his upper lip.
Further material for pseudopogonological studies: slapdash fake beards are nowadays largely the domain of supporting characters and cameo roles, so seeing a lead actor sport one throughout a film is a little disconcerting. Also: the beard seems to be restricting the movement of Lai's face, which is normally pretty expressive, giving him a perpetually glum expression; he looks like a man whose lower face is being strangled by a stubble-parasite. And: the presence of plenty of actors with real beards (unlike in, say, Landru, where everybody has a fake beard) leads to plenty of strange moments, such as a confrontation between Lai and a supporting player who sports a real beard similar to Lai's fake one; Lai, his face constricted, looks a little like the other man's waxwork double.