Depends on what you mean by "spawn". (Your answer is "Yes" and "No".) **If a monster is spawned from a Monster Spawner, then:** Yes it can, as Monster Spawners will always create a mob near the spawner at intervals when the conditions around the Spawner are correct *even if there is no available block to spawn on*, as light is calculated in 3D space. **However, if the monster is spawned naturally then:** No, it does not. Monsters only spawn naturally on [solid][1], non-[transparent][2] blocks at light level 7 or below. The light level at other points above or to the side of the solid block are not taken into account. [1]: https://minecraft.wiki/w/Solid_block [2]: https://minecraft.wiki/w/Opacity