what can be a thesis on Magical realism?

Magical Realism in literature originated in Latin America. It owes some debt to extreme realism (in the arts) which was an intense focus on the "real." But Magical Realism in literature owes more to the development of Surrealism in the early 20th century. Simply put, Magical Realism is the fusion of realistic elements with elements of fantasy, the supernatural, or any others that are not realistic. A famous example of this style is Gabriel Garcia Marquez's short story "A Very Old Man with Enormous Wings." Everything about the story is realistic except for the man with wings. It is a mix of realism and fantasy.
In Dreaming in Cuban, a complicated story about family, politics, and identity, there are realistic and fantastic elements. Celia and Felicia have recurring visions of the deceased Jorge (Celia's husband). Pilar, daughter of Lourdes and granddaughter of Celia, becomes increasingly aware of an inner voice, something that is both a realistic urge to connect with her Cuban ancestry and also something that is magical or perhaps even a telepathic connection between her and Celia, her grandmother.
These magical elements link certain characters together—characters who are separated in time or in space (geographically). And in this novel, the real/magical dynamic is an effective parallel between other dichotomies: Cuba/USA, past/present, as well as conflicts between mothers and daughters. So, while magical elements can be used in Magical Realism simply for the sake of more fantasy, they can also illustrate cultural aspects and how mythic connections arise out of strict realism.