Papua New Guinea's Sir Michael Somare is set to return to Port Moresby this weekend after nearly five months of medical care in Singapore.
This week Sir Michael issued a statement declaring he remained the country's prime minister and intended completing his term.
A month ago Sir Michael was controversially replaced by Peter O'Neill after a parliamentary vote declared his seat vacant.
Sir Michael's son, Arthur, says the return to Port Moresby will allow the veteran leader to attend the early recall of parliament on Tuesday.
Arthur Somare says his father's attendance at that session is critical to a Supreme Court reference that he and other East Sepik MPs have sought following the change in leadership.
"It is absolutely necessary that he be in Parliament on Tuesday because the core question that we have before the Supreme Court is the issue of vacancy itself. The laws of Papua New Guinea are quite clear. If Sir Michael misses three sittings of Parliament then there will be a vacancy, so he needs to make that journey down."