Are you medical discharged or medical retired from the military? The reason why I'm asking is medical discharge doesn't give you Tricare so you only have VA as health insurance but they only cover service connected conditions overseas and its a pain to claim with them. So either have medical insurance or money in case something happens (but usually you have to pay upfront then get reimbursement no matter which insurance).
Visa since you're not at retirement age you can't get retirement visa. Other options would be marriage, education visa, investment visa, or visa run
I read in one of your comment saying that you have rental properties so I assume you have an income. Since visa will be an issue how about being here and there everywhere 3 months or so. That way you could show your son southeast Asia, and once he has reached school-age you can plan something else
oh ok, but which one gives me more days to stay in Thailand? I'm super new to this. Wanna get info before making decisions. Definitely will visit first but I think it's good to know what my options are between vietnam and thailand