Your temporary HP is considered into your Current HP when deciding how much non-lethal damage is required to knock you out.

Think of non-lethal damage as damage to your minimum health level... essentially it raises your '0' HP to be a higher level. Until your non-lethal is greater than your current HP but less than your (base) current HP+temporary HP, your question won't even come up since temp HP is (generally) lost first.

**Generally, if this case does happen, your temporary HP still counts as current HP for keeping you awake when taking non-lethal damage.**

  > Certain effects give a character temporary hit points. These hit points are in addition to the character’s current hit point total and any damage taken by the character is subtracted from these hit points first.

**A *strict* RAW reading** might deem that "These hit points are in addition to the character's current hit point total" does not mean temporary hit points are considered into current hit points, but instead they are their own pool that is not 'current hit points. However, I feel like the word 'addition' indicates that RAI is adding them for a *new* 'current hit point total'.