Originally Posted by
yerffej201
i would think that tickets booked on CX VN site would use VN POS, but any OTA should use US POS. Unless somehow CX can change the POS the fare pulls from even with OTAs
That is not, in general, correct.
Most, although perhaps not all, Expedia sites use a POS inferred from the top level domain. So expedia.fr uses a sales office in Paris. American Express travel does something similar. I imagine if you call a service centre then you will get the sales office for that service centre, but it's possible Expedia does some trickery to get a point of sales at the original ticketing location.
The selling currency is usually the give away: although it isn't strictly required by IATA that a TA sells in the currency of the sales office, I think all OTAs do (?)