@Mick ********
just apply for a non "O" retirement visa from your home country usually done via internet. You could pay an agent in your home country to do this, you will need some documentation over and above passport eg proof of income. This is initially a 90 day visa, once you arrive in Thailand go to your local immigration office get the list of their requirements for extension of stay. Fulfill requirements then lodge paperwork and once it's granted you only have to report every 90 days. There are visa agents in Thailand that for a small amount of money would assist in lodging extension of stay documentation and do your 90 day reporting