Chai Mai Jing Ying Tae

Rin, a recently promoted employee at a direct sales company, loses her job after the company is sued for fraud. Broke and desperate, she meets Ken, a gay crossdresser who also lost his job. When Ken faints on the street, Rin helps him but loses her wallet, which Ken spends. After tracking him down, Rin confronts him, and they end up at the police station. Ken, eager for the prize money from a beauty pageant, convinces Rin to enter. To protect her identity, he renames her Saranya Lertkanlaya (Zin), and she wins, with everyone believing she's a post-op transgender woman. As Miss Queen Beauty, Rin is cast in a TV drama, “Nang Ngiew,” directed by Pak, who eventually falls for her, though he believes she's a transgender woman.
(Source: MyDramaList)