Why does my cat pee in the wrong places right in front of me?

I have a five year old neutered male Siamese. He prefers to toilet outside but has a kitty litter box for when he is inside at night. Quite a few times he will walk up to me and then pee right next to me e.g I've been in the pantry and he walked up and then squatted near my feet to pee; or I'm at the computer and he'll climb on the desk and pee on the table; even once he peed in my sidetable drawer next to the bed!! I have seen him spray outside marking his territory but he isn't spraying near me, he's squatting. The kitty litter is always very clean because he hates it dirty. This behavour happens about once every three weeks.