Did I say I saw it on the internet?
I didn't.
I asked BBL.
And I did something like that. Worked very well. For a couple of 100,000s, and a limited time frame (like a year), any other solution - like what you suggest - is not practicable. Way too much trouble. And the expenses will eat the principal.
I would do it differently if it's many million baht ( @TallGuyJohninBKK sounds good). And if OP is just looking for a solution for his eventual death in 10, 20 or 50 years, in that case the whole thread doesn't make sense.
In any case, and whatever solution, for sums like OP's sums, I would keep the Thai judicial system out of it - as has been said by another poster.
It will be a lot of effort, very expensive, and in the end, the bureaucrats and lawyers will cheat the girl out of her money.
Uneducated, poor Thai girls always lose against the vultures, be it Thai bureaucrats or lawyers from our home-countries. I have seen both. Keep them out.