Both thai shows focus on mutiple characters and their stories/struggles etc.. they have similar themes of jealousy, hatred, revenge, consequences of actions and how things can easily sprial out of control etc and have a similar feel to me. The characters that connect all the story (in GFN Nanno and in AGTTPYH the shop owner) are supernatural and hard to define beings that are seemingly immortal. Girl from Nowhere is alot more episodic though.
The Girl From Nowhere series contains a certain feel and vibe that is present within some of the episodes of On Children. This vibe being a more dark and psychological look on society, using different elements to metaphorically display a person's hidden evil self. It is also similar as in both shows, each episode is set in a different setting.