There is a global standard- the Maritime Labour Convention (MLC) introduced with great fanfare a few years ago and like most things associated with shipping open to a great deal of skullduggery.
This is because many operators on the fringes of shipping are one step away from good old fashioned pirates.
You have dodgy registries whereby the flag of the vessel is powerless and has absolutely minimal standards. Think Mongolia for example, purely a legal fiction.
Then you have coastal states such as the UAE which basically don't give a shit. As many contract workers there are effectively indentured bonds men for the duration of their work permits the UAE government doesn't give a toss for its legal obligations under the MLC and if a couple of dozen seamen wash up on their coast who cares?
Finally the citizenship of the seamen involved comes into play. Some countries make quite a fuss over the mistreatment of their citizens,most don't, including sadly the UK for most of us.
From the seamen point of view it also gets complicated. If the owner doesn't pay your wages the crew can exercise a lien on the vessel which basically means that if its forcibly sold even for scrap the proceeds must first pay out all the crews outstanding wages. However if the vessel is classed as a wreck that doesn't apply. (I maybe wrong on this as it's a few years since I studied maritime law and this kind of thing isn't my everyday work life!)
Also if the crew leave or abandon the vessel they forfeit their rights to claim.
There's loads more I could write but without going into technicalities that's a broad summary.