Polking was in Hanoi on Wednesday to negotiate and quickly reached a preliminary agreement with CAHN.
On Thursday the German-born coach will watch the team train before they play against Becamex Binh Duong in round 19 of the V. League a day later.
He is expected to take over on May 21 for the match against HCMC FC.
Polking managed HCMC FC in 2021 and was expected to take the club into the V. League title race. But they instead dropped to the relegation zone before the league was canceled due to Covid-19.
He parted ways with HCMC after that.
The 48-year-old returned to Thailand, where he has worked for many years, and signed a short-term contract to lead the national team.
After Thailand defeated Vietnam in the semifinal and Indonesia in the final to win the 2020 AFF Cup, his contract was renewed.
At the 2022 SEA Games, Polking took Thailand into the final where they lost to host Vietnam.
Thailand returned the favor by defeating Vietnam in the final to win the 2022 AFF Cup.
In November 2023, following Thailand's modest performance in the 2026 World Cup qualifiers, Polking was sacked.
CAHN contacted coach Polking several times, most recently in December 2023 after their early termination of the contract with South Korean coach Gong Oh-Kyun.
But a possible deal collapsed at the last minute and CAHN used technical director Tran Tien Dai as interim coach before appointing Kiatisuk Senamung.
Due to the club’s inconsistent performance, Senamung resigned on May 14 after four months in charge.
CAHN once again appointed Dai as interim manager but reached an agreement with Polking a day later.
CAHN are a star-studded club with many national players like Filip Nguyen, Bui Hoang Viet Anh, Doan Van Hau, Ho Tan Tai, and Nguyen Quang Hai.
Polking will be the sixth coach in just a year and a half since CAHN were promoted to the V. League after Paulo Foiani, Tran Tien Dai, Flavio Cruz, Gong Oh-kyun and Kiatisuk.
No one has lasted more than four months in the hot seat.
CAHN are currently second in the league with 31 points from 18 games, eight behind Nam Dinh FC.