I'm not sure if the power door lock versions do this or if it's only on manual door locks like mine, but I find it annoying that I have to lock the passenger door & hold the handle up while I close it or it will unlock. If the driver's door did that, I could understand. It might even keep me from locking my keys in the cars, but it makes no sense on the passenger door. So, just like I did with every 80's Toyota I've owned, I had to fix it
Start by taking the door panel off and remove the door latch. If your key is worn out, now would also be a good time to get the key code off the passenger door lock cylinder (take it to a Toyota dealer and they can cut you a brand new unworn key). When you remove the latch this what you'll have in your hands. Start by taking off the little "anti slim jim" shield that covers the mechanism, it's held on by 2 tiny screws

If you play around with the latch a bit you'll start to grasp how it works. The bit we're concerned with is the tab in the red box, this pushes the lock arm back into the unlocked position whenever the latch goes to the "closed" position unless you hold the handle up. I don't like this tab. Cut it off. Oh, and it's a tight fit to get anything in there, I found a half worn dremel cutoff disc works nicely.

this is with the tab already removed, this pic might point out a bit clearer that the one above what need to be removed. reassemble & the door will no longer unlock when you close it and forget to hold the handle. make sure everything is reconnected and works from inside & outside before you put the door panel back on.

BTW, this linkage pivot is slotted so you can adjust where the lock button is when it actually locks the door - about in the middle of the slotted sheet metal should be fine
