Thailand - Spain Dual Tax Treaty Ref Royalty Payments

Earlier this year my Thailand limited company received a royalty advance of 2000 Euros (gross) for licensing a DVD to a Spanish company.

The Spanish customer told me that a withholding tax of 25% is due on royalty payments made by a Spanish company but under the treaty with Thailand this is reduced to 15%. So they witheld 300 Euros and paid us 1700 Euros, which arrived as 80,593.20 THB.

Can anyone tell me how much more tax, if any, we need to pay on this income?

Thanks!