Any credit card transaction is a remittance, as is an ATM withdrawal. The Thai Tax Office only needs to see the transactions, the existence of a CRS agreement doesn't make any difference. The tax liability has more to do with source of the money, your own personal situation, and any DTA Thailand has with your country.
He's probably referring to retirees on pensions, in which case he's correct. Through DTAs many pensions are not taxable in Thailand, and the small percentage that are wouldn't be worth the Thai Tax Office chasing up trying to extract a few baht.