Dream on. Your moving 800,000 baht to Thailand for a visa. You are not going to get much interest. If you want to keep the money in your home country get a DTV visa for a boxing, Thai language, or cooking class.
If you go across the land border yourself, you have to stay out for a few days. If you want to come back right away you need to go with a border run agent who has a relationship with the border office and can pay into the coffee fund
You know, now that someone mentioned it, if you are in Bangkok you can link the skytrain rabbit card to line pay and then using the line app with a Thai phone number, you can get the line wallet and pay using a line pay QR code. Of course you can easily add money at any green line skytrain ticket window
You don't want a bank account in Thailand. It's just gonna open you up to Thai taxes. Stay a tourist and use a wise app virtual visa card and tap to pay