Hi Bucksnet – actually yesterday morning, but yes definitely a flying visit!
capetonianm – I hadn’t really focused on types of interlining agreement, but the page I looked at was definitely about baggage. http://www.thaiairways.com/plan-your-trip/before-you-fly/en/interline_partners_website_link.htm
TimF, I entirely understand they are entitled to refuse -believe me, if I had believed otherwise I would have made much more of a fuss. I am still disappointed, however, that they refused to do so when TG – earning a much smaller fare I might add – were prepared to do it in the other direction on the same tickets. That disappointment became annoyance when they lied to me (I believe) about the absence of an interline agreement. As to the seat allocation, I did complain, and they changed it back – which rather implies that it was not changed for a good reason