Pol Col Amnat Jancharoen, deputy chief of Pathum Thani police, said the protected wild animals were found at the unnamed warehouse in Moo 7 village.
The suspects were Mrs Daeng Srilao, 46, from the northeastern province of Khon Kaen, Prachuap Nooklab and Nawachai Nooklab from the southern province of Ranong.
The deputy Pathum Thani police chief said the animals were transported from Ranong and kept in Pathum Thani pending a trip to the northeastern province of Nong Khai where they would be smuggled to China.
Mr Prachuap said he had bought pangolins from a man named Nai in Sadao district of the southern province of Songkhla. He bought them at 2,000 baht per kilogramme and would sell them at 5,000 baht a kg in Nong Khai. He said that in China the animals' organs were a component of what was believed to be sexual stimulants.
Mr Prachuap said he had done this several times and knew that pangolins had been smuggled from Malaysia.
Pol Col Amnat said each pangolin weighed 8-10 kg and was retailed locally at 40,000-50,000 baht. The price of each pangolin would soar to 100,000 baht in China, he said.
The seized pangolins would be kept at a wildlife rehabilitation centre in Sam Khok district of Pathum Thani before being released to their natural habitat later, Pol Col Amnat said.