How would use of home country credit card or debit card to make purchases in Thailand be classified? Were funds actually remitted to Thailand? ATM for cash withdrawals from home country bank account?

Credit cards and debit cards are quite a grey area, as they are not specified in the Thai income tax law. Under audit, if it is seen that these are being used for day-to-day expenses and living, then credit card usage is likely to be classed as remittance. If you use your debit card, it depends on the source of the funds in the debit account. If it is classified as foreign-sourced income, then it is assessable income.