Soi 3 in the Nana area of Sukhumvit Road was sealed off late last night as 200 police swooped on the area in a crime suppression drive.
News reports stressed that all those stopped and arrested were dark skinned.
Lt Gen Sanit Mahathavorn, chief of the Metropolitan Police Bureau, was joined by the Commander of the Tourist Police division, Pol Maj Gen Surachet Hakpha, as they led a task force of around 200 officers from both divisions down Soi 3 at midnight.
30 Africans rounded up for passport checks and drug testing, six were detained for having no I.D. and testing positive for drug use.
Lt Gen Sanit told reporters the checks were being carried out as part of his divisions ongoing efforts to weed out criminal elements such as drug dealers, adding that passport checks were a good way to catch crooks with a criminal past and any outstanding warrants for their arrest.
Sanit said that the swoop and blockade of the area was part of the Met's ongoing efforts to reduce crime. And he especially wanted to root out those individuals using tourist areas as cover for illegal activities such as drugs related crime.
Checking passports was a good way to do this he reminded the raiding party as this can reveal criminal histories and people wanted on warrants.
He also said that the swoop was in readiness for the ACD summit starting this weekend.
The ministerial level 2nd Asia Cooperation Dialogue Summit, a ministerial level conference, is being held in the city from today until Monday.