The author behind those FIXI novels is a pretty interesting story, actually. It's not one person. FIXI is a Malaysian imprint specializing in urban horror and contemporary fiction, mostly in Malay. They've got a whole roster of writers, kind of like a collective. The one name that always comes up for me is Ruhaini Matdarin, especially her 'Darah' series – gritty, modern vampire stuff set in KL, totally reworks the genre.
A lot of their other writers focus on local urban legends and social issues with a supernatural twist. The imprint itself has a very distinct voice: fast-paced, often quite graphic, and unafraid to blend horror with commentary. So when you ask 'who's the author,' you're really looking at a group of voices shaping a specific corner of Southeast Asian pop horror literature.