[2] In January 2018, Flottmann left Sydney FC due to lack of game time and signed with Thai League 2 club Air Force United.

[14] He played in 22 matches and scored 2 goals On 9 April 2024, Flottmann was signed by Brunei DPMM FC for the 2024–25 Singapore Premier League season.

[1] He made his debut from the starting lineup on 11 May 2024 against Young Lions in a 1–2 away victory where he created an assist for Yura Yunos to score the winner of the game on the 38th minute.

[15] Flottmann suffered a ruptured anterior cruciate ligament in a friendly match a month later which ultimately ended his stint at the Bruneian club.

[16] In September 2015, Flottmann was called up to the Australian under-20 squad for the 2016 AFC U-19 Championship qualification, but he did not make an appearance in Australia's 3 matches.