Normally, I transfer money via De Post bank account, and pay 7 Euro for bank charge.
I can do that on bpo-banking (internet banking), or go to De Post and fill out the money transfer request form.
I prefer bpo-banking which is more convenient and takes about 3-4 working days for money to arrive in the receiver's bank account in Thailand. If you already have De Post bank account, then you can request for use of bpo-banking/international fund transfer at De Post. Don't forget a copy of your ID card na krub.