Myanmar authorities asked to help find fugitives in major cases have detained 81 Thai nationals near the border with Chiang Rai province on charges of illegal entry.
Thai authorities were in contact with them to find out whether one of the men is Pannawit Prathum, who is wanted for the murder of a teenager in Khon Kaen.
Pol Col Ekkorn Bussababordin, the immigration chief of Chiang Rai, said on Monday he was informed about the Sunday night raids by Myanmar police in Thachilek, opposite Mae Sai district.
Myanmar police and officials of the Central Committee for Drug Abuse Control rounded up 48 Thai men and 33 women at entertainment venues and hotels in Na Yao village, about 10 kilometres from the Thai border district of Mae Fah Luang.
None had documents showing they went through the immigration process to enter Myanmar, he added.
They were being detained for interrogation and other procedures at a security office at Mong Hsat in Shan state, about 100 kilometres from the border with Thailand, Pol Col Ekkorn said.
The roundup followed a request from Thailand to help track down fugitives in drug and other cases who had fled arrest warrants. (contnues below)
The red dot shows Mong Hsat in Myanmar, where 81 Thais were detained.
Mr Pannawit, 30, is wanted on an arrest warrant for allegedly ordering the beating that killed a 17-year-old boy in Khon Kaen last month in a dispute over payment for drugs.
Police believe he is the ring leader in the ordering of illicit drugs from a neighbouring country and sale of them online to customers in the North and Northeast. Authorities have not named the country, but it was believed to be Myanmar.
Pornpat Suvannabhum, chief of Narcotics Control Office Region 5, headquartered in Chiang Mai, said they were awaiting confirmation from Myanmar authorities of the identifies of the arrested Thais, including Mr Pannawit.
The process could take some time as many could have sneaked across the border using fake Myanmar ID cards.