Originally Posted by
reiffi
[...] You will not have access to the TG lounge (either F or C).
By the way, I just re-read your statement above and I think this is not correct. As a Star Alliance business class passenger, you have access to any Star Alliance Business Class lounge on day of travelling. So yes, one could gain access to the TG C-lounge in BKK. This is also my experience, had no problem in BKK so far with this (travelling SQ, using TG and vice versa).