transfer Thai Baht to Europe

Does somebody have experience with exporting Thai Baht to Europe after conversion to Euro (or should the conversion take place in Europe)

A good friend came to spend the last 10 years the winter in Thailand and had opened a bank account with SCB where he still has about 400.000 Baht

Now his health has deteriorated and he asks my Thai wife to help : he will send the necessary paperwork to enable my wife to collect the money and that will be no problem.

However I wonder if my wife can then transfer the money back to his account in Europe (it was money sent from Europe before)

Some people are telling us she will need an invoice before the transfer will be approved and this is not possible between private persons