There are scholarly assessments of what Hamlet might be about to say here. I’d suggest that they probably know what they’re talking about – but as the words are not ACTUALLY here, they COULD be anything we want. I want them to be something like:
The King is a thing
That goes ring a ding ding
And sometimes kaching
When the meter’s running.
But I know it is definitely NOT that.
The thing is, though, imagining it to be so would create a very specific way to say the only part that is actually heard. It’s a moment for some possible comedy.