Dependent on one's financial situation, my understanding is one advantage (if one receives a LOT of Thai interest) of having the 15% withholding tax on one's Thailand bank/bond interest, is if if the withholding tax is withdrawn automatically by the bank, then (per Thailand tax law) , that satisfies one's legal tax filing obligations for that interest, and such need not then be included in the assessment whether a Thailand tax return need to be filed. I presume if one's bank/bond interest in Thailand is relatively small, and if one has no other remitted income to affect one's income status in Thailand, then one may wish to consider trying getting back that withholding tax. I don't fall into that category (of qualifying for a return of withholding tax) , so I have never pursued that.