I am not American but do have a US no-fee Capital One 360 account with no international ATM fee and No FX fee. Personally, I would bring the cash and save the 250 baht fee.
The problem with Moreta is it does not support paying non business accounts. Most vendors in Thailand are using Personal bank accounts. So this makes Moreta almost completely useless. The only option for tourists at the moment is the Kbank Pay&Tour prepaid card.
This is hilarious. You managed to miss completely every single point of the post. I was simply pointing out the universal popularity of the PromptPay "QR code" system in Thailand. A tourist without a bank account now has the option of getting the KBank Pay&Tour prepaid card to be able to participate in the PromptPay ecosystem. I also highlighted the downside of the higher FX fee of this product compared to using cash. Finally, I never suggested using a credit card for ATM withdrawals. Simply, paying with a no FX fee credit card when possible is the cheapest option.
No US bank charges $50 per transaction. At Chase it is $5 per transaction. Capital One has the 360 no-fee chequeing account which does not charge an international ATM fee or even an FX fee. Credit card with no FX fee is the cheapest option. People in Thailand don't really use cash anymore. Many people, including myself, pay with PromptPay "QR code". The only place I use cash is at 7-11.
Cash is the best option by far for Thailand. Not only is there a 250 baht ATM fee, the exchange rate will be worse. For large purchases like hotels and airlines then a credit card with no FX fee is best.
Another option now is the KBank Pay&Tour prepaid card. This allows paying with PromptPay "QR code". Which is literally everywhere including street vendors, night market vendors, even BTS. I have a Thai Bank account and in the past 2-3 years have only used cash at 7-11. The only downside is the conversion rate is at the KBank exchange rate which is bad. Thai Baht cannot be loaded directly. For example CAD rate at SuperRich is 23.25 and KBank is 23.93
This is non-sense. I have never been charged a fee to use a credit card in Thailand. My credit card also does not charge a FX fee either so cheaper then cash. For places that take credit cards like hotels and airlines I use a credit card. This will be the major part of travel expenses. You can also link your credit card to Grab and Bolt. So really 20K or 30k cash will go a long way.
This is incorrect. Unless your Visa type dictates otherwise (LTR?) after 180 days you are a tax resident in Thailand. Currently, Thailand is only looking at inbound funds. That could change in the future to include income outside Thialand as well. Any tax treaties will determine if you will need to pay any tax in Thailand. Nothing outside of Thailand will magically make you not a tax resident only how much if anything you may end up paying.
Tax treaties between countries are agreements for exemptions, deductions or credits for taxes paid in one country against owed in another. They don't determine if one is considered a tax resident.