Police said witnesses who were friends of the victim, Anusara, told investigators that they planned to travel to Lan Island with the victim and her boyfriend, Steven Timothy Rowe, on Feb 15.
While they waited downstairs for the couple to pack their backs in an apartment building, Mr Rowe rushed down the staircase and left the building and there were no signs of Anusara.
The witnesses then contacted the police to help find Anusara. The body of Anusara, a Buri Ram resident, was found in a black plastic bag placed on the roof of a restaurant in South Pattaya on March 18.
Police arrested the suspect who was hiding in Udon Thani on Saturday.
The suspect admitted to his crime, according to police, saying that he was jealous of his teenage girlfriend.