I suggest an experiment. Transfer 1k USD or similar using bank and wise. Then divide by rate of the day to see what you really get. My bank is completely opaque regarding exchange rate. Wise is the opposite. So do this then insert what you really would have sent. You can use the wise app using the full amount and they will show you fees. Swift with a bank used to cost me a flat 45 USD for what I'd send but I never knew the exchange rate. I use Wise but we're I to move a lot of money I'd experiment.
I banked my 800k but I used an agent to avoid the lottery of luck and I'm allergic to forms. In Chiang Mai I paid around 30k baht all in all. I didn't shop around, you might find cheaper. As others have said you can do it yourself. I got an O A visa back in the states years ago. Did it all myself, what fun.
As you posted to this group I believe it's okay to say use an agent. You can arrive without any visa and get 30 days. Once you arrive find an agent. This is absolutely the easiest way. I did this. It's not the cheapest way but it is the simplest.
The source of the money just needs to be from abroad. I've read where people just recycle. It's not too hard to live on less than 65k Baht. So a person remits money from Thailand back to their out of Thailand account and then send it back to meet the 65k requirement. Just need to do the math on cost of moving money but I'll bet it's way less than loss of opportunity of the 800k Baht
they will box up your stuff while there. You can just remove some things from a suitcase and put it in another box to meet the weight limit. They actually box the suitcases. For my large suitcase they used 2 boxes which they taped together in the middle. They were very helpful.
they recommended Bangkok bank. I don't recall how long it was. But I arrived on visa exempt and just left it in their competent hands. They responded to email questions.
BTW, 5k of the "around" cost was to open a bank account. They are good about breaking down the costs. I could have spun the wheel to open an account on my own but decided to pay for a sure thing