When we were in Patong for the Kings Birthday, we both wore yellow polo shirts out of respect and had several favourable coments from Thai people.
Respect doesn't cost anything (well, they were Lacoste fakes for 200 each!)
Also, when we went up to BKK, we went to the cinema to watch Casion Royale. Now, having been caught out in the past we remeembered not to get comfy till they played the national anthem so we could stand for it.
There was a farang and his Thai GF sitting in a row in front of us who did not stand up for the Anthem. When it was finished, a Thai girl nearby us went down and had words with them!!