Mr Kilman's Peoples Progressive Party (PPP) is one 16 parties in Parliament and it won just six of the 52 seats.
Vanuatu Independent editor Tony Wilson said the win demonstrated Mr Kilman's negotiating skills.
"Obviously he's very proficient at number counting and number crunching and persuading MPs that he is the way to go," Mr Wilson said.
"The sad news for the people of Vanuatu is that given the state of things, it's highly unlikely that we'll see that government in situ for the next four years.
"We can probably expect to see, perhaps even a number of changes where MPs are persuaded for various reasons to switch camps."
Ralph Regenvanu was one of the successful candidates in the Port Vila constituency and his newly formed Land and Justice Party had a strong turnout in the polls.
He said the election of Sato Kilman was a "disappointing result for almost all of Vanuatu".
"I don't think many people want to see this old government get back in. It's unfortunate that outside is not able to maintain the numbers."
Mr Regenvanu said it was likely there would be a challenge to Sato Kilman's leadership before the end of the year.
"If the opposition decides to put a motion of no confidence in the Prime Minister, they have until the 20th of December to do that, which means it has to go within the next couple of weeks to qualify the notice time."
Mr Kilman's ruling coalition includes veteran MP George Wells, the new Speaker of Parliament, and former prime minister Ham Lini, who will serve as Deputy Prime Minister.
His cabinet also includes Alfred Carlot and Marcellino Pipite, who are still facing charges they illegally boarded a super yacht, the Phocea, before it had been processed by customs.
But Tony Wilson said the return of so many veteran MPs has many in Vanuatu scratching their heads.
"It seemed likely we were going to see some significant change and that didn't happen."
He said part of the problem was that people in isolated outer islanders do not have access to media and communications required to find out what their representatives are doing in Parliament.
"Each election these people return to their islands - often it's the only time they've been seen since the last election - and they come with the promise of bush knives and grass cutters and solar panels, which are gratefully accepted by the people in the villages in these islands who think that's what an election is all about."