I was puzzled as to how this would work as the exit would not be on the main Immigration computer. However it seems that the stamp only had to fool non-Thai Immigration staff who would not have computer access to Thai records...
So I guess that they then just avoided the Thai exit staff on the Bridge with no issues at the Laos side..According to Pol.Maj.Gen. Pallop, the suspect had been offering the fake stamp service to foreign tourists — mostly Chinese and Vietnamese — who wished to leave the country via the Thai-Lao Friendship Bridge. The stamps exempted these tourists from having to have their immigration documents examined when they passed through checkpoints, the officer said.
Pol.Maj.Gen. Pallop said the tourists who sought Mr. Chatchai's service were those who either overstayed their visas or had arrest warrants on their records. Mr. Chatchai reportedly charged tourists 5,000 baht per stamp.