@Daryl *****
I don't know about Thailand specifically but, in general, no country will allow you to have two different Visas at the same time. That would be a bureaucratic nightmare. Even if you could have it I don't think you'd want it because you'd most likely be breaking the terms of one at any given time simply by being compliance with the other. So would you be kicked out? Or allowed to stay? Which would be the priority?
Yeah, after thinking about for 2 seconds there's no way they would ever allow it.