I recommend to apply for a Non O Retirement visa in Thailand. You can get an affidavit about your income at the German Embassy or at a German Consulate, for example Consul Rudolf Hofer in Pattaya.
I also brought my national and international driving licenses. After that, I only had to do 3 very simple tests. 1. Color recognition 2. 3-dimensional vision test and 3. braking reaction test. The 3 tests were in a room and not in a vehicle.