Screening at the border province of Nong Khai has been stepped up after a second alleged Laotian drug lord, Sisouk Daohueang, was arrested in Luang Prabang province last week.
Another alleged drugs kingpin, Xaysana Kaewpimphon, was detained at Suvarnabhumi International Airport in January and is now in Thai police custody.
Nong Khai customs chief Nimit Sangampai said his office had examined records of Sisouk's movements in and out of Thailand through the border checkpoint.
"We have found that Sisouk had entered Thailand many times via the Thai-Laos Friendship Bridge that links Vientiane of Laos with Nong Khai. The latest visit was in January," he said.
In addition, male and female friends of Sisouk had entered the province in around 29 luxurious cars, including makes such as Ferrari, MercedesBenz, Porsche, Lexus and Range Rover.
However after after Sisouk's arrest Saturday, there was further no record of any of them coming to Thailand.
Nimit said that the officials had intensified screening of visitors, with particular attention being paid to topoftherange cars. "We will do our best to carry out inspections so that our work will not affect bilateral ties, as some high-ranking officials and business leaders from Laos also use luxury vehicles," he said.
Thai police believe Sisouk's alleged drug network is larger than that of Xaysana. Both shared a love of expensive cars and led flamboyant lives and were not afraid to flaunt their lifestyles on Facebook and Twitter, posing with vehicles and at fivestar restaurants and outside mansions.