Capital One did well by you on this THB purchase. However, had you had any sort of problem with the transaction, be forewarned that Capital One's Customer Service is notoriously, and inexcusably, awful (poor telephone skills, poor responses by mail, no follow-up, high rates of card rejection while travelling etc. etc.)

I have observed radically different results in different currencies (i.e. a +2% surcharge in the translation of Korean Won to USD). YMMV.

Forewarned is forearmed.