I Told Sunset About You

Development of Part 1 began in December 2019, with Naruebet at the helm. He invited Karakade Norasethaporn and Naron Cherdsoongnern, both of whom he had worked with as fellow students at the Faculty of Communication Arts of Chulalongkorn University, to develop the screenplay with him. Arachaporn Pokinpakorn [th], one of Naruebet's co-writers from My Ambulance, later joined the team. The project was Karakade and Naron's first screenwriting experience; Karakade primarily worked as a writer and editor, and Naron as a flight attendant.

Naruebet envisioned visually rich imagery for the series, and wanted a locale that would serve as an atmospheric backdrop. The writers briefly considered Ayutthaya, as well as several other provinces, before settling on Phuket, which offered the combination of beaches, hills, and an urban environment.With a rough draft for the story, the team conducted a research trip to the Southern island province in late January. They took inspiration from Phuket's multicultural heritage, Sino-Portuguese architecture and local cuisine, and set the story mainly in Phuket's Old Town.Several food items are featured in the story, including the Hokkien noodles sold by Teh's mother and the dessert o-aew, which inspired the name of Krit's character. The names of the characters Teh and Hoon, meanwhile, are from the Hokkien words for tea (茶; tê) and rice vermicelli (米粉; bí-hún), one of many nods to the Hokkien Chinese heritage which forms a large part of Phuket's culture.Chinese culture is also featured in the story through the language (as Mandarin), which plays a central role in the university-admissions plot, contributed to by language consultant Suppawat Zhou. Phuket's pluralism is also reflected through language, with several characters speaking in the Southern Thai dialect and employing code switching during conversation.

The project was officially announced by Line TV at its Line Nexplosion 2020 event on 19 February, under the working title BKPP: The Series. It was originally slated for a July 2020 release.[8] However, production was delayed as the COVID-19 pandemic spread through Thailand in March, just as work was entering pre-production.[9] After one of its actors tested positive for the virus, Nadao closed its office from 20 March and advised its staff to self-isolate.[10] The writers, who had until then had almost daily face-to-face meetings, continued working via conference calls, and used the time to further refine the screenplay. A first read-through was held with lead actors Putthipong and Krit via Zoom video call on 24 April, after which some further refinements continued, totalling about ​5 1⁄2 months of screenplay development.