Marriage visa vs retirement visa

I am currently working and I qualify for a retirement pension next year. I have met someone in Thailand that I would like to marry. I plan to visit Thailand later this year and I am considering to initiate marriage then. My goal is to become a Thai citizen to qualify for health care asap as taking out private health insurance long term would be very expensive or prohibited due to some pre-existing health conditions. I am getting married primarily because of the quality of the relationship, rather than for other reasons.

What do you consider as the best route to establishing long-term pathway to living in Thailand in my situation, preferably to include public health care. My pension will pay about 38,000 baht a month and l could get over the 40,000 baht threshold with bank interest payments.

I believe it takes 3 years to get citizenship in Thailand, does this have to be spent continuously living in Thailand, or can I spend a year after marriage in my own country to settle all my affairs and travel to Thailand every 6 or 3 months during this time. What do you suggest is the best pathway for me. Thanks in advance.