Chaiyuth Kamkhun, deputy director of the department, said Customs officials spotted two Thai women travelling from Hong Kong on May 10. They were wearing watches of the Swiss luxury brands Audemars Piguet and Patek Philippe and were pretending that they were personal belongings, and not being brought into the country for commercial purposes.

But the Customs officials suspected that they were smuggling the watches into the country and trying to evade the 5-per-cent tariff.

Chaiyuth said the two women had confessed and were subject to legal charges, but later they posted their stories on social media, accusing officials of exceeding their duties.

Customs officials said that before the department took legal action against the two women, tax officials had received a tip-off about the smuggling of watches for online sale in Thailand. The suspected smugglers had sent packages of watches from Hong Kong to Thailand via international postal service.

The market value of the two watches was Bt1.3 million before tax or Bt1.5 million after import and value-added taxes.

According to current Customs regulations, a traveller can bring in goods worth no more than Bt20,000.

Customs officials at Suvarnabhumi Airport over the past two years have caught 239 smugglers with goods worth a combined Bt233 million, Chaiyuth said.