90 days is easy as there a few ways to get a 90 day stay without leaving Thailand (Tourist Visa (and, currently, Visa Exempt), 60 days + 30 days extension, Non-O over 50 (90 days)). Will you be visiting once a year or more because the Non-O over 50 plus the 12 month extension might suit such a plan?
What new Visa requirements. If you mean the TDAC from 1-May you complete it within 3 days of entering Thailand sp 72 hours before right down to a few minutes before.