Ratchapoom Boonbunchachoke, director of A Useful Ghost, met the audience of Hong Kong via Zoom!

The director shared that Mae Nak, a female ghost in Thai myth, was one of his inspiration. Pregnant Mae Nak was forced apart from her husband by war. Before her beloved returned home, she died in childbirth and became a ghost who remained to guard their home. Upon returning home after the war, the husband remained oblivious to his wife's demise and continued living with her as a human-ghost couple, provoking discontent among neighbours. Re-examining the legend, the director discerned that this human-ghost relationship was profoundly "queer", both parties were not accepted by society. He thus sought to reinterpret this tale through a contemporary lens.

The film touches upon the relationship between mother-in-law and daughter-in-law, with the mother-in-law hailing from Thailand's northeast region. Coming from a poor background, she does not speak standard Thai. Ratchapoom noted that most characters in the film are marginalised people in society, willing to sacrifice their morality for acceptance. The female protagonist who reincarnated as a vacuum cleaner and her mother-in-law are both outsiders in the family, trying to fit in. The conversation between the two in the end reveals that both are grappling with similar dilemma.

Dust plays an important role in the film. Ratchapoom shared that Thai was seriously affected by dust pollution when he was writing the script, hence he incorporated some real life elements into the story. In Thai political slang, "dust" is also refer to insignificant person. Finding the metaphor apt, he employed dust as a symbol.

Ratchapoom revealed that he had conceived the film title before finished writing the script. Despite deciding the title would be A Useful Ghost, he was indeed uncertain what constitute a "useful" ghost. He shared that in Thai, ghost that appears in people's dream is deemed useful. When he finished his first draft in 2020, protest broke out in Thai. Mobile phones of protestors were confiscated and their personal chat records were used as evidence by the police. Taking inspiration from it, he created a ghost that is useful to the authority, entering others' dreams, invading the private realms of others.