I'd say above-human-average DEX (15 or so maybe), below-human-average STR and CON (penalties for being so tiny, between 8 and 11 perhaps) and absolutely abysmal charisma (charisma means ability to influece humans and humans in Amn consider goblins something to be attacked on sight). If he decides to join your PC, and disobey a direct command from a superior, he must be smart enough to independently think the possible consequences of his actions without the aid of elder goblins and goblin shamans who usually tell what to do. That's quite a feat in a goblin society where weird adulthood rituals usually weed out the potential anarchists at an early stage. So the mental stats would be more than those of other goblins.
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