Just some updated (??) information from the Chatuchak Transportation Department:
I had my appointment for 5 years driving license renewal last week and was also very much concerned about this test as I struggled with it in the past.
While being in the queue in the "examination room" I noticed that they have now some written english instructions on all the testing stations and I was already glad when I saw that they apparently only wanted to test the Green and Red colors when doing the peripheral vision test which would have been ok with me as I struggled to differentiate between Green and Yellow in the past.
However, to my great surprise and might I say relief, the actual test only involved to tell the examiner on which side the (light white/gray) light was turned on!! This is of course is much easier and actually maybe also makes a little bit of sense to test to see if somebody can see anything in their peripheral vision.
Done for nearly 6 years now again with all this BS....;-)