I sit here, it is early morning after being awakened by a knocking on my glass. I heard it several times during the night, each time I jumped out of bed to check if someone was at the glass sliding door that leads to our bedroom. In fact, as the sun was rising, I heard it again but this time much louder. I realized it was a bird that clicks-clicks simulating the noise of a coin knocking on the window. If you have the chance to be in the neighborhood.
If you want to know more about birds or go bird watching: http://www.thailandbirdwatching.com/Contents/448692-bird-leaders.html