Opaque green tea, what is that? If you order green tea in Thailand you get a long drink in a plastic cup that resembles a sweet, frozen shake. (Then you can put the cup in a plastic bag, hang it on the steering rod of your motorbike, drive around and sip it with a thick straw on hot days.)

The Thai green tea is very different from Japanese and Chinese (usually hot) green tea. The Thai drink is light green and completely opaque.

I read that Thais use "green tea powder", condensed milk, "oriental spices", crushed ice and more to produce this shake. 

When I drink this I remember having been served "similar" in Japan. Opaque, green tea in small clay cups. Much more filled with "small particles" than is "normal" tea.  It was hot and not sweet, at least as I remember.

When I Google I just find entries like Oolong tea which is not what I am looking for. Oolong tea is clear and more resembles traditional tea.

My question mostly relates to what I have had in Japan. What is this brew that is green but differs very much from "normal" green tea by being opaque?
If it's &quot;green tea powder&quot; it's probably matcha.

Matcha is finely ground powder of specially grown and processed green tea. It's special in two aspects of farming and processing: The green tea plants for matcha are shade-grown for about three weeks before harvest, and the stems and veins are removed in processing.
The traditional Japanese tea ceremony centers on the preparation, serving, and drinking of matcha. In modern times, matcha has also come to be used to flavour and dye foods such as mochi and soba noodles, green tea ice cream and a variety of wagashi (Japanese confectionery).


The drink you had in Thailand is probably an iced matcha shake of some sort, made with condensed milk.  In Japan, the drink is served by itself as part of tea ceremonies and is opaque even without milk added to it.
There's a guide to how tea ceremonies work and the process of making tea here, if you're interested.