You need paperwork from the place you’re going to be using. It already needs to have been paid for and they have to send you specific documents for your DTV application. It can’t just be a general interest you have in unspecified activities.
You need to have chosen what the activity is before you apply for the visa
Many, usually anonymous, who report questioning or other difficulties entering Thailand on a DTV tend not to mention their previous immigration history as well.
it’s not a new immigration act. They just temporarily stopped asking people arriving by air to fill out the paper forms. Now it’s back and is an online process.