What type of visa should I apply for to retire in Thailand and work on my fiancée's farm?

Been looking at posts for visas now for a while and still unsure which is best for me. I'm thinking Non O as I have the following plan for retiring in January to fiancées farm in Issan -

I'm 54, had heart attack in Dec 2020 so will have insurance up the wazoo. Cannot claim pension until June '22 but even then will leave that to accumulate in UK bank. Already built little house and have plans to marry 2022. Want to help ON farm growing, planting and harvesting crops, but not OFF farm selling etc. Could go Elite visa but a lot of money to pay upfront. Have money to cover Non O-A visa but seems a lot of extra hoops to jump through for similar benefits to Non O.

I have NO plans to return to UK in future. Likely arriving on exempt status then within 10 days doing the following, if still relevant:

-Apply for the Non-O visa (2000 baht)

(wait 20 days)

-Go back, get the Non-O and new 90 day stamp inked in

(wait until you have 45 days or less left on that new stamp)

-Go back apply for the year extension (1900baht)

Then every year after that apply for a new yearly extension

Any constructive or alternative comments will be greatly appreciated.

Thanks and stay safe.