@Johan *************
Unfortunately, many people do not understand very simple things.
Having a valid visa does not automatically give you the right to enter the country. The final decision is made each time by the immigration officer at the border. And if the officer questions on what basis you are still using a DTV under the Soft Power category when your activity ended, for example, a couple of years ago, that is something you will have to explain.
That is exactly why the claim that “it is enough to enroll in a course once, and then you can freely travel for five years” is a very dangerous misconception. Yes, the visa itself may still remain valid. But if the immigration officer concludes that you no longer have any real grounds to stay in Thailand under the soft power activity on which that visa was originally issued, they may simply refuse you entry.
At the same time, it is important to understand that even now we are already hearing many complaints like: “Officers at the border asked a lot of strange questions and advised people to change their visa.” They ask those questions and make such recommendations for a reason. Usually, it is because the officer has doubts that the person still genuinely fits the original purpose for which the DTV was issued, or believes that the visa is no longer being used for its actual intended purpose.