I'd recommend you to go to a local Chang fixing electric. And let him build one like this. This one I right now don't use but it's good for a few thousand watt. I use it with some Powertools.
Krungsri has a very good currency exchange rate. Maybe the best. On top you can take 50.000 with a visa or mastercard in 24h. I am with Kasikorn very happy, very good app. But they didn't allow me to open a second account. Everything is smooth so far.
With Bkk bank I had different trouble, friends of me too.
What you got to do is going from bank to bank, branch to branch. A few do it. You have to find them. Sounds crazy but that's how is the situation for farangs in Thailand right now.
If it is too long offline the sim might be locked. To reopen you need to go to a store dtac or true and if the number is not already with a new owner you can reactivate it.