That's my guess too. Imagine you transferred 65,000 baht monthly for your visa, but received only 55,250 baht in your bank account, and then you would have to prove with a, into Thai translated and by your embassy certified, document from back home, to overworked, barely English speaking Thai revenue bureaucrats that your money has already been taxed. Expect not to have use of your money for the next 2-3 years... You can as well write it off as a 'donation' for Thailand.