Police inspected Bangkok's Nana area, along Soi Sukhumvit 4, early on Friday morning as part of a campaign to prevent and suppress trans-national criminals.
The operation followed complaints that the Nana area had some criminals among tourists, Pol Maj General Surachet Hakpan said.
The 2am operation, which checked foreigners for alleged illegal entry or overstaying visas as well as testing for drug abuse, was to boost tourist confidence.
Police checked 80 tourists (14 males and 66 females) most of whom were African nationals. They found that 66 tourists had passports - six of whom (one German and five Nigerians) overstayed their visa - while the rest (four males and 10 females) did not have a passport.
Charges were filed against the offenders. One Namibian national tested positive for substance abuse.