The International Weightlifting Federation (IWF) said in a statement lifters shall not compete at the Tokyo Games, regardless of the change of date.
The Olympics have been postponed for a year due to the coronavirus outbreak and are now scheduled to be held from July 23 - Aug 8 2021.
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The Thai and Malaysian federations can appeal the IWF ruling to the Court of Arbitration for Sport (CAS) within 21 days.
The IWF also imposed a $200,000 (£153,000) fine on the Thailand federation (TAWA), which had already voluntarily banned itself from all weightlifting, including the Tokyo Games, because of its recent doping record. The IWF said:
Half of it is imposed as a penalty, the remainder shall be used by IWF to offset IWF costs already incurred in connection with the TAWA matter and for additional IWF testing of TAWA athletes.
Eight Thai weightlifters, including two reigning Olympic champions, tested positive for banned substances at last year’s World Championships.
The Thais were caught when the IWF carried out extra tests in Cologne, Germany, on samples taken last November from "target athletes" at the World Championships in Turkmenistan.
The country was also involved in a doping scandal in 2011 when seven teenage girls were banned after testing positive, two of whom are among the six new cases.
The IWF suspended TAWA's membership status for three years, saying the sanction will be reviewed on or after March 7 2022 if "TAWA can demonstrate it has met pre-defined criteria".
In January the entire board of Thailand's federation resigned less than a month after allegations of doping by child weightlifters were made in a German TV documentary.
The Malaysian Weightlifting Federation has been suspended for one year. The sanction will be reviewed and may be lifted as early as Oct. 1 2020, the IWF said.
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