Thank you so much, Tony. What a comprehensive guide to the ports of call - telling us what exactly what we wanted to know.
It was particularly useful to learn that there are shuttle buses in most of the ports. When we phoned Seabourn to ask about this, they told us that we would have to wait to find out once we had boarded - not much use when we wanted to book trips in advance. It almost makes me wonder if this lack of advance information is a ploy by Seabourn to encourage us to book their excursions.
We had already more less decided not to bother to go to Bangkok for the reasons you state, and also because we spent a few days there relatively recently, so a wander round Pattaya sounds like a better alternative. We too intend to book independent tours but had not yet decided which company to use, so will go for Viator, as you appear to have been satisfied with them.
Thank you again for all the information and advice, which will be really useful. It makes me wonder why some of this could not have been provided to us by Seabourn.