Bangladesh Premier Sheikh Hasina was accorded a warm welcome upon her arrival at the Government House, the Thai premier's office
SI Md Akhter Ali, in-charge of Maddhaypara Police Outpost, lodged the case on Wednesday, according to Baghaichhari Police Station OC Manjur Alam.
Forty to fifty unidentified men have been accused in the case, he said.
On Monday, unidentified gunmen in Rangamati shot the election officials dead after the end of second phase of the Upazila elections boycotted by an organisation of Chattogram Hill Tracts people.
At least 11 others were injured when the gunmen carried out the attack in Noi Mile area on Baghaichhari-Dighinala road.
The next day, another group of gunmen shot dead Upazila Awami League president Suresh Kanti Tanchanga in another attack in the district's Bilaiichari upazila.
No one has been arrested in the two incidents.