Is there an adjective for someone who can withstand ridicule?

Solution 1:

good sport

someone who can accept a loss in a competition or can accept being the butt of a joke.

It is used as a noun. The definition is related to being able to take a joke but it also covers accepting criticism with grace.

As an adjective, I would say easygoing. This would describe the type of person.

relaxed in manner or attitude; inclined to be excessively tolerant

As a phrase, there is have a broad back:

not be easily hurt by criticism

It helps to have a broad back in showbusiness.

But this goes back to thick-skinned:

not easily hurt by criticism, insult, etc.

As you said, thick-skinned has two meanings. One of the meaning is what you ask but the other one is what you want to avoid. It would depend on the context then.

Solution 2:

Unflappable can be used to describe this kind of attitude:

not easily perturbed or excited or upset; marked by extreme calm and composure; "hitherto imperturbable, he now showed signs of alarm"; "an imperturbable self-possession"; "unflappable in a crisis"