Thacker is one of two new directors, along with Richard Simkin of Stockport County, appointed following a vote.
Aldershot Town chairman Shahid Azeem regains his position for a third term, while Barnet chairman Anthony Kleanthous departs.
The announcement was confirmed at the National League’s Annual General Meeting.
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Clubs also voted to introduce a salary cap for the 2022/2023 season and clubs voted for the National League to form a standards/ethics committee.
Meanwhile, the number of clubs relegated in the National League this season will be reduced from four to three to take the total up to 24 teams from the following season.
There has been no change to the league structure in the National League North and South from the 2020/21 season.
To accommodate an increase to 24 clubs in each division from the 2022/23 campaign, three clubs collectively will be relegated from Step 2 to Step 3 and replaced by eight promoted teams, the National League said.
Clubs were informed the 2021/2022 season will not begin without fans or suitable grant funding.
Jack Pearce, National League chairman, said in a statement: “A contingency is also being discussed, should the season not be completed in its entirety. The league will be meeting with clubs to finalise these arrangements.
“The league also recognise that there is still disquiet from many clubs in a number of areas and the league are committed to meet with all clubs to address these issues in the very near future.