Absolutely not necessary to obtain a non O retirement from visa exempt or tourist visa entry.
You are living in Thailand with annual extensions. Very simple process.
Your friend initially had a Non O-A visa and that along with extensions requires insurance.
He could kill off his Non O-A and do as you did in obtaining a Non O at his local immigration office..
UK, USA, AU do not supply embassy "letter"
Siam Legal are currently not assisting with opening bank accounts..