Does working for an international organization (like a UN agency) enhance the chance of getting a UK visit visa ? I have been refused twice before and would like to increase my credibility for the third application.
You have serial refusals for your UK visa applications, but you are desperate to get in to the UK anyway and your premise is to sit the PLAB examination. You are asking if taking a job at the UN will improve your credibility for your next UK application.
Does working for an international organization ( like a UN agency ) enhance the chance of getting a UK visit visa?
The answer is 'yes', having a job of any sort is an improvement in your personal circumstances, more so if your job has professional standing on an established career path.
The follow on to your question is:
will this change in circumstances carry the application?
Probably not unless you have been doing for a long time. They tend to worry when a person's history shows a fixation on getting in to the UK. This concern is exacerbated by the fact that the PLAB exam (Part 1) is available in countries that you can get to much easier than the UK.
I have looked at your previous questions here in our archives and the answers you got remain valid; you can still use them as a basis for developing a visa strategy.
And of course if you are issued a UN passport, then the problem is solved because the UK honours diplomatic credentials from the UN, World Bank, IMF and so on.