Hi there - here's a quick summary, I'll try to put together more later.
Thank you to everyone for their advice and input, all of it was helpful.
BKK - I was only there two nights so didn't have chance to experience much. I went to Obsession (ladyboy bar) and found it a bit intimidating. I think it must have been a quiet night as I was surrounded!
I had more luck off ThaiFriendly and Grindr (for boys and ladyboys). A had one great session with a boy who came to my hotel - very hot and active both ways. Around 2K including tip.
Pattaya - had a couple of ladyboy encounters from bars with rooms on site, on Soi 6. One great, one less so. Both around 1.5k.
One guy at my hotel which was pretty good and one boy in his room who was super hot. Both from Grindr. The area around Jomtien beach has plenty of bars, but I didn't like them much. But that's just personal taste - there were loads of hot boys around.
I also went to Sansuk sauna - it was ok, but not brilliant.
I'll definitely be back!