The Myawaddy-Mae Sot border has seen fewer travellers and stricter security at both ends after the deadly explosion in Bangkok on Monday.
The number of Myanmar nationals returning from Bangkok has fallen, maybe because of the heightened security, said a police officer at the Myawaddy Friendship Bridge.
A Myanmar expatriate in Mae Sot added that the vehicles entering Thailand were now being inspected more thoroughly than before.
The Myanmar Embassy in Thailand has warned migrants to be cautious. It is estimated that more than a million Myanmar nationals are working in the Kingdom.
However, Than Aye, a worker in a plastic factory in Samut Sakhon province, said: "There are no restrictions in our area. It's business as usual."
Thai police are seeking co-operation and support from Malaysian border police to help arrest the key suspect, who may have crossed the border.
Pol Colonel Kan Thamakasem, superintendent of Narathiwat immigration checkpoint, said he had given Malaysian immigration officials a sketch of the suspect and told them that there was a Bt3-million reward on his head.
Kan said he had instructed immigration officials at the Narathiwat border checkpoints of Tak Bai, Waeng and Sungai Kolok to step up checks on people crossing into Malaysia.
In Chiang Rai, immigration officials have also stepped up checks for the suspected bomber, who could use any of three routes to escape into Myanmar through Mae Sai, Chiang Saen or Chiang Khong districts.
Sketches of the suspect have been put up at the checkpoints to help the public identify him and inform the police.
Nong Khai Governor Suchart Noppawan said he had received an urgent order to step up security at all government sites and tourist attractions in his province. Four 24-hour checkpoints will be set up on major roads, and at border checkpoints, Thai and Laotian immigration officials have been instructed to step up checks for the suspect.