If Jagdeo become un-retired and serve as Prime Minister then retires again. Does he get the Presidential scale or the Prime Minister one. Or both? 
Technically he was already substantive Prime Minister for like 2 days which of course according to Guyanese law makes him eligible to the Prime Minister's pension. But of course you are only entitled to 1 pension.
The law assumes that one draws the pension of the highest rank of the pensionable state offices.
However, you are not entitled to both pension and the salary of the same office at the same time. One can serve again in the same office and receive the "excess" differential if your pension rights entitle to some higher "excess" amount.
The law has some hint of sense in one single respect. It technically bars double dipping. Ironically American law in NY specifically allows double dipping.
So the only reason he would want to re-enter the fray is for the purpose of tiefin?