Just had a result with my Debit card.
Called BBL help line 1333 , after the " Press 1 etc fiasco " I got lady speaking excellent English.
Explained about my card being no good for Internet purchases .
She looked into it and apparently it was the Debit card company that had put a block on my MC / Union Pay debit card.
So she cancelled my card and I had to go to my Bangkok bank to get a new one ( free of charge )
I returned home with my new card and tried to use it online , no , card same as before " Cannot verify "
Called 1333 and explained everything and the lady told me that I need to unlock my card for Internet payments.
The unlocking of the card can only be done through the 1333 help line.
She calls a number then I just followed the instructions , bit long winded but there you go.
Any way , tried my card today and everything was okay ( on Amazon ).