@Elías *******
Tried to use one when I was on my old visa on my way out of the country to apply for my DTV a few months ago.
Actually, I didn't even want to use it. I prefer human interaction and a stamp. I was re-directed there initially by staff but it didn't work. So I went back to an officer who stamped me out, which is much better anyway.
I thought the autogates only work for those who've arrived into Thailand without a visa?