The Immigration Bureau today (Dec 15) asked foreign tourists to understand the situation, which could result in congestion at passport control, reports the Bangkok Post.
Enhanced security measures apply mainly at Suvarnabhumi, Don Mueang, Chiang Mai, Phuket and Hat Yai airports, Immigration Bureau spokesman Pol Maj Gen Choengron Rimpadee said.
Senior police were closely monitoring the situation he said, citing growing concern in the face of renewed and intense clashes between Thai and Cambodian forces following the collapse of the latest ceasefire.
There was a possibility that foreigners might exploit the visa-free entry scheme to carry out operations that threaten Thai security, Pol Maj Gen Choengron said. It was most unlikely that Cambodians would come here for tourism at this time, he said.
Cambodian nationals entering for valid business purposes are required to obtain proper visas from the Thai embassy.
Another focus group is passengers from eastern Europe and northern Asia, who might be hired as a mercenaries, or even as spies, Pol Maj Gen Choengron said.
The waiting time at immigration control queues could be extended from the usual 20 minutes to around 45 minutes. This would not affect Thai travellers. Commercial flights between Thailand and Cambodia were still operating as usual, Pol Maj Gen Choengron said.