Non O along with ongoing extensions based on marriage and retirement do NOT require insurance.
Extensions retirement are extremely simple. Very little paperwork.
The major negative is financial requirements that basically locks up 800k baht.
Extensions marriage require lot more paperwork along with possible home visit, witnesses (some offices) , under consideration period, photos etc etc.
Plus side is minimal financials.
400k in bank for only 2 months prior to application then can be used after final stamp in pp