I agree. There may be illegal ways to get around the rules, but they involve risk. Not just the risk of losing they money, but the risk of going to jail.
I've been trying to solve a similar problem (wife rather than GF) and based on the feedback I got here and elsewhere, here are my conclusions.
1/ Avoid anything illegal - it involves the risk of losing the money, and going to jail.
2/ Avoid will and probate and anything that have to do with Thai legal system; it takes forever, it is expensive, and the results are not guaranteed. Besides, there is a risk of the GF's family getting involved and succeeding in getting some or all of the money in question.
3/ Joint accounts are out (because of the immigration requirements for EOS), and in you case, being a GF, she can't be a joint signatory (at least that is my understanding).
4/ The only bullet-proof way to make sure she gets the money in case of your death, and she gets all of it without any delays, it to keep the money in a bank account in her name. However, for this to work, two things have to be true:
- She has to be 100% trustworthy. With 1 mil in her name, she can take the money and disappear, and you have no recourse whatsoever.
- Assuming that the funds in question are the money that you are currently using to satisfy the financial requirements for the retirement-based Extension of Stay, you would have to switch to the income method and show foreign-sourced THB 65,000 per month deposited in a Thai bank account.
At this point, I am strongly leaning towards the option #4 myself.