A documentary about the pain of mothers losing a connection with their children might not sound like one of the most uplifting films of the year, but Kristof Bilsen’s film is a radical achievement: a love letter to loss, sacrifice and yearning. It questions how we care for elderly loved ones, makes provocative contrasts between east and west in the economics of medicine, and, with a central character who’s pure charisma, this is intimate observational documentary-making of a high standard.

Pomm is a carer in Thailand for westerners with Alzheimer’s. She gives her patient one-to-one care, which comprises singing, joking, hugging and confiding, as well as the basics of cleaning and welfare. This is more personal attention than would be possible in her patients’ home countries, and though it doesn’t come cheap, families feel it’s worth the expense of sending someone halfway across the world for it. When we first meet her, Pomm’s patient is Elisabeth, who can communicate only in squeaks and other noises, but seems calm and content.

Pomm has her own problems, primarily lack of contact with her children who live many miles away. Tender late-night confessions to Elisabeth make clear the extent to which the support is mutual.

Facebook Twitter Pinterest An exploration of pain and dignity … Mother. Photograph: Limerick Films

This is a brilliantly novel way to establish characters’ motivations and doesn’t feel crass. It’s natural and born of their trust in Bilsen, whose presence in the room appears to be minimal. Pomm and Elisabeth are each other’s family, bound by their need for one another. A segue to Pomm’s relationship with her children feels uncomfortable – she’s out of their sight and out of their minds, and it hurts. Later, Pomm has another patient, Maya, brought from Switzerland by a family who love her but have decided the greatest love is to let her go and put her in the hands of a stranger.

With Maya’s arrival in Thailand, the film shifts up a gear, moving from tenderness and sensitivity to something much harder to watch, and Bilsen deserves praise for doing it. Earlier scenes with Maya and her family in the mountains of Switzerland are puzzling and even alienating, as we are plunged into their world without any context. We’re intrigued but feel like intruders on their private foreboding as they know their time together is running out. Bilsen’s plotting from start to finish is immaculate, never explaining too much but always hinting just enough about the melancholy destinies of the characters.

Mother explores pain and dignity, and the way that some people’s pain is considered more important than others. Pomm has lower status, only begrudgingly granted time off by her boss to see her family. No one asks her about her wellbeing, no one dotes over her. Yet she is the hero of this piece, giving everything for strangers, night and day, in an exhausting service so her own family can be cared for.

This is an original piece of work, addressing the selflessness of mothers and the impact of dementia on families. These subjects have been the focus of documentaries before but rarely in this combination and with such an unflinching resolve to keep filming in uncomfortable moments.