Yes we can corroborate that an onward flight is being made a requirement. At least in Phuket. We had a similar experience with one of our long time Muay Thai students and DTV holders who had never been questioned before. You can read our blog post here about it. Yes many are still entering without any questions but more are being asked for certain details. Here the blog post
*********************************
This is a blog post and meant to be a form of advertising but it includes helpful information as well. Hopefully it helps someone who is unsure what may be asked when re-entering.