Voters in the seat that covers North Burnett, Western Downs and Banana Shire will go to the polling booths on June 18.
Callide takes in farming areas, coal mines and one of the state's biggest coal-fired power plants.
While climate change, energy and mining have dominated political debate in the seat in recent years, the LNP's Bryson Head says he's campaigning to improve health care.
"I'm not okay with the prospect of a colleague of mine at Dawson coal mine having an accident and waiting hours for an ambulance, because they're sitting here at Rockhampton waiting to offload their other patients," the 26-year-old told reporters on Monday.
"That's why I'm standing up here as the LNP candidate for Callide, because I'm going to fight for a better health care system for everyone in the bush."
The Callide by-election was called after Mr Boyce successfully ran for the federal seat of Flynn.
Premier Annastacia Palaszczuk says Labor will field a candidate while Katter's Australian Party has selected Adam Burling, who polled third as an independent in the 2020 state election.
Mr Burling offers voters an alterative to the two major parties on policy areas such as net zero emissions by 2050, leader Robbie Katter told reporters on Monday.
"We pursued him on the basis that he's performed really well in the past, and that he has the ... character profile in terms of having that mining background and rural background," he said.
Mr Katter described the contest as a tough mountain to climb given the region's previous support for the LNP.
"A lot of people there will be trying to get rid of a Labor government, and all I can say is we're committed to doing that as well."
One Nation's Sharon Lohse is also expected to contest the seat.
Callide covers a vast agricultural area, at least four major coal mines, a number of coal seam gas projects and the Callide coal-fired power station.
The LNP holds the seat with a margin of 15.8 per cent.
Nominations for the by-election close at noon on Tuesday.
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