No, you don't have to file a report in every country. Fraud reports are processed by the offender's country. Our report has already been accepted by the Vietnam police in the offender's city. If you file a report in your country, nothing will happen. If you file a report in the perpetrator's city, it will. That's why there are so many crypto scammers. Because users can't reach them or choose the wrong route.
We have reported MecaCex for intentional fraud through various methods, including market manipulation and embezzlement of customer funds/coins. All with evidence. He has defrauded countless users. He has stolen liquidity from crypto projects and sold the coins on other markets. And so on.
Well, you are right but that isn't completely accurate. You can file a lawsuit for international fraud, but it hardly ever comes to an end. As you said, it's far better to do it in the country of the scammer, however, most people don't even know which country the scammer is in. Do you include people from other countries, making it an international fraud/ scam scheme, and not only for the Vietnamese clients? IMO it will be helpful.