As per the PRD for the Hat of Disguise:
Pathfinder Reference Document wrote:
This apparently normal hat allows its wearer to alter her appearance as with a disguise self spell.
Hat of Disguise at PRD
So, with this we find that the Hat works as if the "Disguise Self" spell.
As per the PRD for the "Disguise Self" spell:
Pathfinder Reference Document wrote:
You make yourself—including clothing, armor, weapons, and equipment—look different. You can seem 1 foot shorter or taller, thin, fat, or in between. You cannot change your creature type (although you can appear as another subtype). Otherwise, the extent of the apparent change is up to you. You could add or obscure a minor feature or look like an entirely different person or gender.
The spell does not provide the abilities or mannerisms of the chosen form, nor does it alter the perceived tactile (touch) or audible (sound) properties of you or your equipment. If you use this spell to create a disguise, you get a +10 bonus on the Disguise check. A creature that interacts with the glamer gets a Will save to recognize it as an illusion.
Disguise Self at PRD
In the spell description it is mentioned that if you use it for a disguise, you get a +10 while using this spell. However, it also mentions that you can change your gender, and it says you can appear taller or shorter (to a small degree). It also says you may appear as a different subtype.
Type must be Humanoid (Cannot change this) These monsters below are examples of being humanoids with other subtypes. (Note, these are not to be confused with Monstrous Humanoids, which is another type.
PRD Monsters by Type wrote:
boggard, bugbear, cloud giant, cyclops, dark creeper, dark stalker, derro, drow, drow noble, duergar, ettin, fire giant, frost giant, gnoll, goblin, hill giant, hobgoblin, kobold, lizardfolk, merfolk, ogre, orc, stone giant, storm giant, svirfneblin, tengu, troglodyte, troll, wererat, werewolf
Monsters by type (Look for "Humanoid")
Hope this information helps.
EDIT: I just noticed this was a necropost, but I'll leave this up in case someone stumbles upon it, just like I did. Thanks.