His agent, Andrey Grushin, said the football governing body refused to hand out any punishment to the 28-year-old Vietnamese goalkeeper.
In January this year, Muangthong claimed to FIFA that Lam had terminated his contract with them prematurely to join Japanese side Cerezo Osaka.
But Grushin said Lam complied with FIFA regulations when leaving Muangthong since the club had not paid his salary, and he considered it a breach of contract.
According to FIFA rules, players are allowed to walk out on clubs that are two months late in paying their wages.
Muangthong claimed they had only deducted 30 percent of players’ salaries due to the Covid-19 pandemic with permission from the Football Association of Thailand, and the players would get that amount later, and so technically there was no breach of contract.
After the club filed the complaint, FIFA gave Lam a temporary transfer permit to join Osaka.
The Thai club has seven days to appeal the decision.
Lam, who played major role in Vietnam's recent regional successes including the 2018 AFF championship, is currently under treatment for a serious shoulder injury he suffered last month and is expected to take at least four months to recover.