The overloaded Immigration Bureau is seeking police outside its organisation to help with passport checks at Suvarnabhumi airport.
It is also asking passengers to arrive well ahead of their boarding times to ensure they will not miss their flights.
Pol Maj Gen Natthorn Phrosunthorn, chief of Immigration Division 2 which supervises five international airports in the country, said some passengers at Suvarnabhumi airport have missed flights because there are not enough immigration officers to check passports before flights depart.
The number of passengers passing through the airport every day has risen while the number of immigration officers has dropped as some have been promoted or sought transfers to other organisations to avoid the heavy work load.
"On Feb 11, the problem was particularly serious because as many as 387 non-commissioned immigration officers took leave for a commissioned officer examination.
"That caused very long queues at the airport," Pol Maj Gen Natthorn said.
About 150 officers from elsewhere in the Immigration Bureau were deployed to the airport, but they weren't able to help much as they were inexperienced.
Pol Maj Gen Natthorn said another problem was that Airports of Thailand Plc was modifying areas in the passenger terminal to improve security, which had halved the number of immigration booths.
He plans to deploy 70 female riot police officers to assist on the desks tomorrow and later recruit more immigration officers to help meet demand.
He hopes the congestion will be relieved further next month when an automatic passport check system is installed. "We are very tired...many immigration officers want to leave the organisation because they cannot rest and are in very risky situations. If they rush and let through fake passports or wanted criminals they can be jailed," he said. The Immigration Bureau has 1,312 positions for officers at Suvarnabhumi airport but there are only 1,045 officers. Newly recruited officers are still being trained.
Pol Maj Gen Natthorn asked passengers to arrive at the airport earlier so long queues will not cause them to miss flights.
Suvarnabhumi airport director Somchai Sawasdipol said fast-track immigration booths for first-class and business-class passengers would be removed so staff there could help handle regular passengers during peak hours.