It takes only a few strategic bars of tinkly piano score to suggest that the protagonist of How to Make Millions Before Grandma Dies (Lahn Mah) might trade his cynical motivation for selfless devotion before the end credits roll. But the unapologetic sentimentality doesn’t make this bittersweet comedy-drama any less touching or insightful in its observation of spiky family interactions when end-of-life issues and questions of inheritance cause sparks. Thailand’s submission for the international Oscar is the country’s first entry to make it onto the 15-title shortlist.

The debut feature from television and documentary director Pat Boonnitipat was a blockbuster in its domestic release, crossing borders to find similar success elsewhere in Southeast Asia and grossing an estimated $73.8 million worldwide. It’s easy to see why. Viral social media exposure that sprang from Manila theater staff handing out tissues prior to each screening and audience members posting videos of themselves in floods of tears on the way out no doubt helped.

But what’s perhaps more significant is the perceptiveness and affection with which the screenplay by Thodsapon Thiptinnakorn and Boonnitipat captures a family dynamic that’s complicated and imperfect but grounded in a loving sense of intergenerational duty, even if concerns of personal benefit can get in the way. In the story, that dynamic is very specifically Asian, but the basic plot mechanics are sufficiently universal to resonate anywhere.

The theme of death is established with a welcome lightness of touch in an opening scene set on the day of the Qingming Festival, when families of Chinese origin visit the graves of their ancestors to clean the sites, scatter flowers and make ritual offerings of food and incense. The religious holiday matters most to Mengju (Usha Seamkhum), the crotchety grandmother of the title, fondly addressed as Amah by her family. She’s bossy and frequently critical of them, mostly with good reason.

Her eldest son Kiang (Sanya Kunakorn) is a financial trader whose wife and daughter chime in via video call, prompting Amah to point out that they never visit her. Her youngest son Soei (Pongsatorn Jongwilas) is a deadbeat with a gambling habit. The middle child is careworn supermarket worker Sew (Sarinrat Thomas), the most dutifully attentive of Mengju’s three children. However, the fact that Sew’s son M (Putthipong Assaratanakul, aka “Billkin”) has dropped out of college with the pipe dream of making money as a videogame streamer seems to reflect badly on Amah’s daughter.

When the old woman expresses her wish to be put to rest in a grand burial plot, the awkward responses suggest that none of her family will be volunteering to foot the substantial bill. While still at the cemetery, Mengju has a fall and is taken to hospital, where an examination reveals that she has stage 4 stomach cancer. The family decides to keep the grim news from her.

Meanwhile, M studies his savvy younger cousin Mui (Tontawan Tantivejakul) as she cares for their wealthy paternal grandfather in the final months of his life and then inherits most of his estate when the old man dies. Mui swiftly sells his house and moves into a modern high-rise apartment, where she sidelines as a sexy nurse on OnlyFans. She advises M to insinuate himself as Amah’s primary carer and get into pole position in her will, telling him he’ll stop noticing the “old person smell” after a while.

M starts turning up unannounced at his grandmother’s house in one of Bangkok’s Chinatown districts, where she makes a humble living selling congee at a local street market. Mengju is immediately suspicious of his motives, proving resistant when he tries to ingratiate himself with her, which prompts M to break the news of her cancer diagnosis.

Mengju accepts the prognosis with stoical calm and drops her objections when M moves in to take care of her, accompanying her at 5 a.m. each day to her congee stand. Even so, she’s an irascible woman who’s set in her ways and determinedly self-reliant, which makes her prickly during the next weekly family gathering, when even Kiang’s wife Pinn (Duangporn Oapirat) and daughter Rainbow (Himawara Tajiri) make a rare appearance.

It soon becomes apparent that almost everyone hopes to inherit Amah’s house, especially as her condition worsens and chemotherapy fails to produce results. Hard-working Sew (Thomas is the standout of the supporting cast) is the only one who cares for her mother altruistically. She’s more pragmatic than self-pitying when she observes, “Sons inherit money, daughters inherit cancer.”

The patriarchal imbalance and the tendency in traditional Asian families to favor sons — who carry on the family name — over daughters play out effectively both in developments with Mengju’s estate and in the grandmother’s own history.

In one lovely sequence, M takes her to visit her well-heeled older brother (Wattana Subpakit) and his family in their palatial home. It’s a cozy reunion, enlivened by the elderly siblings doing karaoke, until Mengju asks him for money to buy her funeral plot. She reveals to M that despite caring for her parents in their dotage, they left their entire estate to her brother, partly because of their low esteem for the husband they had chosen for Mengju in an arranged marriage.

The heartfelt movie is ill-served by an international title that suggests broad comedy — the original Thai title, Lahn Mah, means “Grandma’s Grandchild,” which comes much closer to capturing the story’s emotional center.

Even if Jaithep Raroengjai’s score leans into the sentiment, M’s growing fondness for Amah — and vice versa — is conveyed with a depth of feeling that steers it clear of the trap of formulaic schmaltz. Their bond slowly supplants his earlier opportunism. And surprising developments in the final act build to an affecting conclusion in which the sadness is mitigated by unexpected rewards.

Strong ensemble acting makes the family a believable unit, their differences notwithstanding. But it’s the evolving rapport between M and Amah that makes the film so captivating, played with humor and sensitivity by Assaratanakul — also a successful T-pop singer and Gucci brand ambassador, drabbed down in sloppy slacker gear for this role — and delightful newcomer Seamkhum, a natural in her first feature. The 78-year-old actress was signed to a modeling agency after being spotted on video in a dance contest for seniors and has been seen primarily in commercials.

In addition to eliciting solid work from his cast, the director imbues the movie with a vivid sense of place, working with DP Boonyanuch Kraithong to mark dividing lines of wealth in various Bangkok neighborhoods, notably the historic, traditionally Thai Chinese Talat Phlu community where Mengju lives.