You may be right that Thailand does not track the money, but you are responsible to tell them, and tax fraud might be punished, all up to you if you want to take that risk.
money brought in by creditcard is also bringing in money. It does not need to be cash. And living in Thailand, not working in Thailand, and not bringing in money from outside looks quite suspicious, don't you think?
Visa and tax are unrelated to each other, when you are 180 days or more in total in a calendar year in Thailand, you will be considered tax resident, and might have to pay taxes depending on your situation, but not on your visa.
ATM from foreign account is bringing in money, taking cash with you is bringing in money. How well everything can be checked is another story, but be aware that you are supposed to live from something, so you should tell you bring in some money when you are tax resident and have no Thai job.
Anonieme deelnemer Thailand not even sees it as work, because on DTV there still is the remark "work prohibited". And when it is not considered as working in Thailand, the income cannot be local sourced, so until you stay 180 days or more, and bring the money in, you might have to pay tax for it.