Movies that use our remembered love of the cinema experience of our youth can’t help but be sentimental. From “The Last Picture Show” to “Cinema Paradiso,” “Four Hundred Blows” to “The Fabelmans,” filmmakers have found that their nostalgia for the Magic of the Movies resonates with many a film fan.

Films about the Third World version of that experience are often built around a traveling cinema that shows movies to remote villages in India — where this still happens, as “The Cinema Travelers” and other films remind us — and elsewhere, a way of bringing filmed entertainment to the off-the-grid/pre-TV-set-in-every-home masses.

“Once Upon a Star” is a Thai variation on that theme, with a Thai twist in the way this “truck cinema” was presented in villages and towns like Lopduri and Nakhem Sowen and Phitsanulok. It’s a very slow, faintly romantic drift into sentiment and nostalgia that could benefit from a little cutting for pace, just so long as you don’t edit out the “sweet.”

Manit (Sukollawat Kanarot) heads a truck troupe sponsored by Hermit Holder Playing Cards and Osotthepuayada Pharmaceuticals. Aged driver Man (Samart Payukaroon) and hunky young concession stand operator Kao (Jirayu La-ongmanee) travel the backroads and mud-paths of 1970 Thailand, taking care to avoid communist-controlled “Red Zones,” showing their movies to those without electricity, TV or cinema.

The Thai twist to all this is that the films aren’t projected with sound. It was cheaper to hire “dubbers,” actors who’d “perform” the film, and during “commercial” breaks, plug the patent medicine that they were there to sell, their real reason for being on the road.

Their corporate overlords are quite strict. Manit has to do all the dubbing, no matter how often “Hey, is that supposed to be a GIRL’S voice? (in subtitled Thai, or dubbed) is shouted from the peanut gallery. He drops the needle on records that provide the background music, and vocalizes such sound effects as he deems necessary.

But by 1970, audiences were demanding more, and competing troupes have multi-voice casts, including women, putting Manit’s crew at a terrible disadvantage. Kao might be an aspiring actor himself, but he can see the real problem is not having a woman on their dubbing team.

A newspaper ad brings lovely Rueangkae (Nuengthida Sophon) to their attention. She’s evasive about her experience, and her personal past. But she’d love to make money to go to typing school so she can become a secretary. She’ll do. She instantly ads credibility to their endless cycle of “dubbed” dramas and action films starring Thailand’s most popular actor, Mitr Chaibancha.

But as Manit and Kao both take a shine to the woman they call “Kae,” you can see where this is going. Piecing together her back story via hints and a few drunken admissions doesn’t really scare either of them off.

There’s good if not swooning chemistry between the leads, and the portrait of Vietnam War era rural Thailand is novel. A cute touch in Nonzee Nibibutr’s film is the selection of banjo and yodeling Thai “country” music on the soundtrack, which gives the movie a jaunty touch which the pacing and self-seriousness of the story doesn’t capitalize on.

Yes, the quartet has seen the black and white TVs in the larger towns they visit. Yes, some traveling cinemas are already shifting over to projecting with sound.

Manit’s “You’ve got a bright future ahead of you” speech to Kae is either blinded by love, or just a lie.

There’s enough material here — encounters with soldiers and monks and rural rednecks, the possible love triangle, dub-offs with their arch rivals and the like — that this picture could have bounced by, never pausing to get mired in the mud, which it often does.

A lighter touch — it really wants to be a sentimental, downbeat comedy — might have made this yodeling Thai melodrama sing. As it is, it only hums along here and there, carried by its sweetness and superficially developed characters.

Rating: TV-14, profanity, smoking, drinking

Cast: Nuengthida Sophon, Sukollawat Kanarot, Jirayu La-ongmanee and Samart Payukaroon

Credits: Directed by Nonzee Nimibutr, scripted by Ek Iemchuen. A Netflix release.

Running time: 2:!7