Security is being heightened ahead of the two-year anniversary of the Erawan shrine bomb blast on Aug 17 as authorities believe members of the Muslim Uighur ethnic minority are still seeking ways to carry out reprisal attacks.
The bombing of the shrine at Ratchaprasong intersection on Aug 17, 2015 killed 20 and wounded 130. Another explosion took place at the Sathon pier the following day, but no one was hurt in the incident.
Yusufu Mieraili, then 27, and Bilal Mohammed, then 31, also known as Adem Karadag, both ethnic Uyghur Chinese, were accused of being involved in the bomb attack. They were later arrested and detained at a Thai jail, pending trial.
Critics said the bombing was the probable result of the government's decision to deport 109 Uighur migrants back to China in July 2015.
However, the government played down the theory, saying efforts by Thai authorities to suppress a network smuggling Uighur migrants through Thailand to a third country could have been the motive behind the blast.
Following the deportation, the Thai consulate in Istanbul, the Turkish capital, was ransacked by Turkish protesters, believed to be right-wing nationalists, angry at the Thai government's decision to repatriate the refugees who many say face persecution in China.
A security source told the Bangkok Post the army and police were ordered to provide stringent security throughout this month.
Uighur networks believed to be involved in human trafficking and hiding out in Thailand will also be monitored as authorities suspect the group still holds on to anger and is likely to create unrest, the source said.
After the deportation of the Uighur migrants two years ago, Thai authorities have continued to arrest Uighur migrants entering Thailand illegally, the source said.
So far 61 of them have been placed in custody. The source denied to reveal the details of the arrests.
"We must not let our guard down, and have to come up with preventive measures. The Uighur people are upset and could cause problems," said the source, citing intelligence reports.
Citing the increased security measures, the source said police and army officers will not only be deployed to key venues or tourist attractions, but they will also focus on gathering intelligence.
The source said Uighur groups have been under the authorities' radar since the bombing.
Authorities are keeping a close watch on human trafficking, illegal entries and other transnational crime networks which may hold a grudge against Thai authorities for clamping down on syndicates producing fake passports and documents, the source said.
The source said officials also detected movements among a network smuggling Syrians into Thailand, noting security authorities are concerned that IS militants could use this channel to hide in Thailand. Efforts will be ramped up to crack down on the network, the source added.
Meanwhile, security officials are also worried the Thai political situation could fuel unrest, the source said, noting violence may also erupt from political groups or southern insurgents.
"We are keeping an eye on those staging unrest in the South as they could come out of the three (southernmost) provinces to carry out incidents.
''They may seek to exploit political turbulence as verdicts of several key court cases with the political implications are being passed this month," said the source, adding attacks may be launched to mislead people into believing they are the results of a political problem.
"People should help serve as the eyes and ears of their communities to ensure security," the source noted. Anyone who behaves suspiciously, including foreigners, should be reported to authorities, the source added.
However, the Immigration Bureau said it has not received warnings about foreigners intending to stage terror attacks in Thailand.
Immigration Bureau chief Nathathorn Prousoontorn said it is not possible for Uighur groups to carry out attacks in Thailand as none have entered Thailand since a major crackdown several years ago.
There have been no fresh arrests of Uighur people, though some are still in the custody of the bureau, he said. They cannot be sent overseas because no country will receive them, he noted.
He said the illegal entry of Syrians is unlikely as they need to seek visas before coming to Thailand.
They are subject to stringent checks by the foreign ministry, he noted.