@Srey ******
Most countries that offer 5 year multi entry visa have more restrictions, like Schengen visa with maximum 90 days in a 180 days period to prevent using it to live in the country.
Not implementing checking mechanisms indeed make abuse predictable.
The problem they have is what to do with somebody who has the intention to do Muay Thai training for lets say 3 years.
Unreasonable to ask for showing a 3 year pre paid contract.