I suspect immigration will want you to prove you are still engaged in the activity you signed up for, in order to extend. So, a two- week cooking class, or a couple of medical appointments might not do. We'll see.
If you travel in and out of Thailand regularly, or semi-regularly, the DTV would seem to be a good option. If you stay in Thailand most of the time, you're just making yourself take more trips -- either to immigration, or out of the country.
Also, the DTV does not require you to apply from your country of origin. You can apply from any number of nearby countries.