I came when I was 40. I have been here 9 years I will be eligible for the retirement visa in a few months (yippie).
Basically to stay in Thailand long term you will need to
- get rich
- get married
- get a job
- get a kid
- be a volunteer
They've recently expanded the 'get a job' category to include technical people. I almost fit into the SMART category except the company work for is not publicly traded and it's unlikely they'll provide all the paperwork the Thai government requires.
So far I have had a few marriage visas (same wife 1.5 years), volunteer visa (1 year), work visa (1 year), a few covid extensions. The rest of the time (5.5 years) has been tourist visas.
You can only do two land border bounces per calendar year, but you can do as many by air as you like.
An immigration officer once told me an ED visa looks suspicious for a person 40+.. I think its a culture thing.
If I were in your shoes I would look at spending
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my time in Indonesia (Bali) and
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my time in Thailand. I am fond of Bali, but you may like any other city.