you are absolutely wrong. If your foreign license is not in English then you have to have it translated and sent to your embassy for verification. Then you may go with your documents to get your license. If I am correct if you have a German drivers license it is not in English, so you have first have it translated. Before you post a comment you should know the facts. To many people post wrong information.
The only one that is valid is a Thai License. First go to immigration and get a residency certificate (300TBH). Go to a doctor and get medical certificate (200TBH). Take your passport and forms to Land and Transfer office. Arrive early. Before 08:00 am preferably. You also will need your US valid License. Watch video ( 1 hour) and then do some simple tests. Pay fee and wait for your Thai License. If you are lucky you will be finished by 12:00 otherwise after lunch.
Go to an approved driving school. One is called Myron. They charge approximately 1500 THB and they do everything. It takes 5 days to do but not 8 hours per day. They do practical and classroom instruction. They also do the testing both on bike and exam. Then they give you all paperwork to go to Land and Transfer office. Just go with a medical certificate and certificate of residence and pay the fee. EASY