Zoran Jankovic has been appointed coach of the national U23 side, the Football Association of Thailand said on Thursday.
The move came after Worrawoot Srimaka, who guided the team to the SEA Games title last month, informed the FAT that he wanted to be only an assistant coach of the side.
Worrawoot will now be Jankovic's assistant, while Milovan Rajevac, coach of Thailand's full national team, will be adviser to the U23 side.
Serbia's Jankovic is also an assistant coach to his compatriot Rajevac in the senior national team.
The Thai team will next play in the AFC U23 Championship in China in January.
Worrawoot on Thursday had a meeting with FAT technical cheif Witthaya Laohakul.
"We would like to thank Worrawoot who only wants to be an assistant coach of the team," Witthaya said.
Witthaya initially wanted Rajevac to also take charge of the U23 team but the Serb turned down the offer as he wants to focus on the senior national team.
Meanwhile, Spencer Prior has quit as coach of the Thai women's team after they could only finish second at the SEA Games last month.
The Englishman was appointed coach of the Thai women's team in May last year.
He steered the team to win the 2016 Southeast Asian title and qualify for the AFC Women's Championship which will be held in Jordan next year.
Thailand were favourites to win the gold medal at the Kuala Lumpur SEA Games but missed out on the title due to their inferior goal difference to champions Vietnam.