The High Court in Glasgow was told Khanikporn Satjawat was at an HIV conference at the city's SECC with friend and colleague Qounjai Channarong, 43, on November 11 and 12, 2012.
Miss Channarong claimed Miss Satjawat had complained over dinner the previous night that her conference security pass had been checked a lot.
She said that when they went to a lecture the following afternoon Miss Satjawat went to the toilet and after around 20 minutes when she hadn't returned, she started to worry.
The jury heard Miss Channarong looked for her colleague and later found out she was dead.
Miss Channarong was giving evidence at the trial of Clive Carter, 35, who is accused of murdering Miss Satjawat by repeatedly striking her on the head and body with a fire extinguisher at the Clyde Auditorium, on November 12, last year.
He has admitted the culpable homicide of Miss Satjawat and has lodged a special defence of diminished responsibility, but the Crown did not accept this plea.
Carter, from Motherwell, North Lanarkshire, is also accused of committing a breach of the peace at a Glasgow hotel a week earlier.
The court was told Miss Channarong and Miss Satjawat -employed by Bristol-Myers Squibb as product managers - arrived in Glasgow from Thailand as part of a group of delegates.
Miss Channarong said that on their first day at the conference they registered and each received a welcome pack, including a security passes with their names on them which they wore round their necks.
She told the jury that while out for dinner that evening Miss Satjawat, known to her as Nong, spoke to her about the pass.
Advocate depute John Scullion asked: "Did Khanikporn Satjawat say anything to you during dinner about security passes?" She replied that Miss Satjawat told her that her badge was checked on "many occasions".
Asked if Miss Satjawat said who checked her pass, the witness said that she hadn't mentioned who it was.
Mr Scullion read a part of the witness statement Miss Satjawat had given to police the day after Miss Satjawat was killed.
The jury was told she said: "During dinner Nong mentioned that she kept getting her security badge checked by a security guard, the same one all the time."
She was asked about the statement and if it would have been more accurate than her evidence in court but she said she could not confirm.
The witness was asked again if Miss Satjawat said if it was the same security guard that checked her badge and replied that Miss Satjawat had not mentioned it being the same person that checked it.
Carter denies the charges.
The trial before judge Lord Matthews continues.