Usually spelled tokay in English, it's ตุ๊กแก in Thai. I've seen a couple and heard a lot upcountry. They are large enough to give a good scare if you see one indoors, but generally stay outside, unlike their smaller green cousins you see all over. Here is a wikipedia article including an ogg sound file which sounds exactly like what I heard every night outside my bungalow in Nan. I quite enjoyed the sound.