Two Malaysian nationals were detained on Monday near the Thai-Cambodian border in Aranyaprathet district after it was discovered they had no entry stamps in their passports.
Muhamed Ruzaini, 23, and Muhamud Yusup Yinahut, 23, were detained at a security checkpoint on Suwannason Road near Klong Luek police station in Aranyaprathet district, said Pol Col Benchaphon Rotsawat, head of Sa Kaeo's immigration office.
The two men claimed they forgot to have their passports stamped.
They told police they had entered Thailand via the border checkpoint in Sadao district of Songkhla and drove to Sa Kaeo to buy used clothing at Rong Kleau border market.
The distance from Songkhla to Sa Kaeo is 1,153 kilometres, or an approximately 15-hour drive.
The two were detained while travelling in a pickup truck with Malaysian licence plates to the Thai-Cambodian border, Pol Col Benchaphon said.
Both claimed they ran businesses selling secondhand clothes in Malaysia.
Pol Col Benchaphon said investigators were not convinced by their story because the cost of travelling from the Malaysian border all the way to Sa Kaeo just to buy old clothes did not make sound business sense.
"If they really wanted to buy used clothing as claimed, it would have made much more sense and been much cheaper for them to stop and buy them in Bangkok, where there is plenty of secondhand clothing to choose from," he said.
Police suspected the men had other reasons to attempt a border crossing into Cambodia, he said.
Police are running criminal background checks on both men, who have initially been charged with entering the country illegally.
