A quick holiday to Vientiane in Loas and you can apply online from there. Only takes a few days to get if you have the required documentation to load onto application
Apply for non o retirement visa in your home country is a good start. Then on day one or 2 go to your local immigration office in province you want to live in and ask for their requirements for extension of stay. Do what they ask. Non O visa does not require health insurance however if you get 6 months of travel insurance before you leave home country it gives time to sort out Thai health insurance