Absoulty impossible to do. How would anyone know if the bundle of cash you have in your suitcase is from a taxed savings account or a columbian shipment of coke?
Correct which is why anyone shipping money in right now and prior to next year to buy a house/car/health insurance/veneers etc etc is certifiably nuts! whatever it's costing you, add at least 20%
You're putting a lot of faith in the thai authorities being up to speed with over 200 DTA's coming at them all at once! I've got a feeling EVERYONE will get taxed regardless and the onus will be on you to make the case to get a refund. Also different countries individual tax year ends (ie UK April, Thailand December etc) are going to cause carnage imo