You can get a O-A (retirement) in your home country. You have to do a medical and police clearance first, and prove financial ability by producing a bank statement or something. This is proof of money in your home country, no need to have money in a Thai bank. Getting the O-A retirement multi entry in your home country I have always found the easiest. It is already a retirement visa, no need to convert. Leave the country and re-enter, border run is fine -no additional re-entry permit required, before expiry date of visa and you will be stamped in for another year. (last time I was actually stamped in for an additional 18 months, must be my good looks - Effectively, the visa will then cover you for two years, no additional costs or financial proof requirements.
Seems that few people are aware of this.