A Town Like Alice (1956), directed by Jack Lee.
After WW2 a English woman returns to a small village in Malaya to build a well and thank the people there for sheltering her and others during the war. Most of the film is a flashback to the Japanese invasion and the horrific treatment of a group of women prisoners.
Said to be inspired by true events. All these "woman prisoners of the Japanese" stories (I recall the Tenko series and Paradise Road) have common features: the shock of the sudden collapse of British resistance, the contemptuous brutality of the invaders, the heat and deprivation, with the women's clothing becoming ever more stained and ragged, and a long series of deaths.
The distinctive features of this one:
The romantic framing story: Jean keeps running into an Australian soldier, also a prisoner.
The endless marching. There is no camp for the women so they are permanently on the road.
The children are not spared.
The prettiest of the women has had enough and volunteers to be a comfort woman. She gets in a car, is driven away and we never see her again.
The crucifixion of the Australian boyfriend, nailed to a tree. This is not explicity shown, but the setup is wrenching enough
Of the Japanese: one is exceptionally cruel, one is exceptionally kind, and the others just practical and without sentiment. The Malayans are more warmly portrayed.
Jean Anderson (Miss Horsefall) was also in Tenko 25 years later.