NAKHON RATCHASIMA, Thailand, Dec 13 (Reuters) - Vietnam's Austrian coach Alfred Riedl has quit his post after the under-23 side suffered a humiliating loss to minnows Myanmar at the Southeast Asian Games, Vietnam's soccer federation said on Thursday.Riedl, hugely popular in Vietnam after steering the team to the quarter-finals of this year's Asian Cup, stepped down after his team's penalty shootout loss to Myanmar on Tuesday. "After the result of the SEA Games match, Mr Riedl talked with Vietnam football officials and later announced he would no longer be coach," said a federation official, who asked not to be named. Riedl was not reachable for comment. The elimination in Nakhon Ratchasima proved to be the final straw for Riedl, who has seen his teams knocked out of qualifying stages for the 2010 World Cup and the Olympics in the last month alone. The Austrian, famous for his no-nonsense approach, was in his third stint as Vietnam coach since 1998 having previously been fired for speaking out against the communist country's state-run soccer federation. The former Austria Vienna, FC Metz and Standard Liege striker has been hugely popular in Vietnam and had dozens of fans offer to donate money or offer a kidney to him when he needed a transplant earlier this year. He found a local donor and has since made a full recovery. Assistant coach Mai Duc Chung will replace Riedl on a temporary basis.