Do they pay you to write this stuff?
None of the lounges that I have been to in BKK is brilliant. The difference between the CX business class (which britra already has access to) and the first class is not great.
If CX really cared for my loyalty they wouldn't give me less than half the miles I get from AAdvantage for the same flights (largely in business class). This is far more valuable than being able to use CX's business class lounge when I am flying on another airline.
I use CX because their inflight service is the best. But the Marco Polo Club is one of the weakest loyalty clubs out there.