If I remember swab test will take atleast few hours to get the result and it is much expensive test kit needed to do that so it is not actually possible to swab test every person enters into the casino and also social distancing will not be possible in any casinos so government should allow the casinos to work even if they know it will result into spread just for economy gain or they should completely close it.
Is this even practical? Labs are overwhelmed and they should be rather testing those individuals who are showing active symptoms of COVID 19, rather than wasting their time on people who visit casinos. And another thing is that these tests are not 100% accurate. Here in India, there have been cases of individuals with symptoms testing negative during the first test and later testing positive.
This is not a solution and no country will agree to that. Test are too expensive and if that would be applied for casino visitors then many other businesses could request the same. Besides, like you've said, there is no guarantee that results are fully correct. Self discipline of people and to obey medical recommendations is the key but that is very hard to achieve.