The electorate of Lockyer, between Ipswich and Toowoomba, would be the "jewel" in One Nation's crown, a political expert says.
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And One Nation leaders believe they could win up to a dozen seats in the next Queensland Parliament.
The seat was held by One Nation's Bill Flynn until Mr Rickuss won in 2004 as a member of the National Party.
One Nation founder Pauline Hanson narrowly lost to Mr Rickuss by just 114 votes, after preferences, when she stood at the 2015 election.
Senator Hanson said Lockyer represented "what One Nation stands for" in terms of the rural sector challenges.
"Small businesses out there are shutting down, you've got the changing face of Australia that is happening out there," Ms Hanson said.
"I hope it's a seat that we can win because they are struggling.
"I think there's a great possibility at the next state election (that we'll win Lockyer), and I'll be putting all my efforts in to win that seat."
It was an effort that would have a chance of paying off, says Griffith University political expert Paul Williams.
Dr Williams said One Nation would likely have targeted Lockyer anyway, but Mr Rickuss leaving would create a vacuum.
That meant, Dr Williams said, One Nation could be expected to claim the seat.
"If the LNP is preferencing One Nation and not Labor or a popular independent, then that seat will go to One Nation," he said.
"(Lockyer) will be the jewel in their crown. I think they'll really try and win this seat."
Dr Williams said it was possible One Nation could get six to 12 seats in the next Queensland Parliament, depending on how the LNP decided to preference.
He said it would be wise for the LNP and One Nation to choose candidates who were "well-connected locals".
One Nation eyes off "10 to 12" Queensland seats
One Nation Queensland secretary Jim Savage said the party could definitely win Lockyer.
Mr Savage said it was not yet decided how many seats One Nation would contest, but he believed winning 10 to 12 seats was "not un-doable".
"Every seat that we will be contesting, we'll treat every one as a winnable seat and we will chase it with full vigour," Mr Savage said.
"But certainly, Lockyer is the prize seat, it was the seat that Pauline Hanson came within an absolute whisker of winning last time and we will be going full out.
"We fully expect Lockyer to return where it truly belongs, with One Nation."
Mr Savage said One Nation's candidate for Lockyer, to be announced soon, had a background in farming and in business.
On Monday, Opposition Leader Tim Nicholls said it would be important to get a good LNP candidate "on the ground in a relatively short period of time".
Senator Hanson said she did not think One Nation would lose momentum if the state election was not held until 2018.
