Some of the confusion may be due to the "authorities" trying to deal with two sets of people:

1. Thais returning from hot-spots, like Korea, from which ~ 5,000 Thais have already returned, with perhaps as many as a 100,000 waiting to return. These folks are working in Korea illegally, so in addition to amnesty (from Korea Imm), the jobs are gone so nothing else to do but return.

2. Tourists, arriving from or via (transit) the six hot-spots. The Tourism Authority of Thailand is strongly discouraging tourists from coming from these six countries. Without some extra-judicial means, or by invoking special powers (martial law, which Thailand has some experience with), it may not be "legal" to forcibly detain foreigners once Thai Imm stamps them in?

Until more of the iceberg is revealed it would be crazy to travel to Thailand.