What should expats know about renewing visas by leaving and re-entering Thailand?

Alfred Hitchcock comes to mind 👍

There's no such thing as a visa that you leave to renew. In fact there's no such thing as renewing a visa at all.

You can apply for an extension of stay which is always a brand new application, not a renewal.

If you are talking about a multiple entry visa, you do not renew anything with these either. If you leave and return you receive a brand new entry stamp under the visa.

Every entry into Thailand is at the discretion of the immigration officer that you are standing in front of. If the officer believes something about the visa is off, or that you are abusing the system in some way, you might be subject to questioning and could possibly be denied entry. Because of this, no one can tell you if you're going to be admitted to the country or not.

When/If the DTV is approved the terms and conditions will be harsh