For a gambler's mindset, why should they undergo a swab test just for the purpose to enter the casino? If I'm a gambler I'd rather find other casinos with no restrictions like that unless I'm a die-hard player of the said casino. It's no different from other establishments wherein there is no need for a test.
Swab test is necessary if your place was in the high virus-infected record, but if the place that has flatten curve record of virus-infected and if they are in a modified general quarantine level, so this is a case to case basis. Thermal testing and proper guidelines for sanitation or disinfectant will be fine.
Though it is risky for gamblers to do this, I guess if they really want to they will find ways just to gamble.