You can’t beat bringing in cash- but limit is normally usd 10k. So my concern there would be issues involved taking more than that. I’ve never declared excess cash but you’d have to do it leaving own country which I think with bank statement and proof or source ok.
However you should declare it thai side- there the very risky bit as I’d not like any thai touching a large amount of my cash in a situation they can make up rules.
Now I strongly advise against unless you can afford to lose it, but the walking through security nothing to declare is amazingly relaxed.
Just got my embassy visa letter on collection of passport. It asks to fill in when my last entry visa was to move it. Not my latest visas that are to me the relevant ones. Does it matter when I arrived in thailand? I may leave it blank and ask them what they want to put in that box.