Chulalongkorn University ranked top among Thai universities in the latest rankings which also saw two tertiary institutions in Singapore breaking into the world's top 15 for the first time.
But overall, the three Thai leaders performed worse than they did last year, with overall rankings 10-50 notches lower.
CU retained its lead at No. 253 in the world's rankings in 2015, down 10 places from last year, according to the QS World University Rankings released on Tuesday.
Mahidol University came second at 295, down from 257 a year ago.
Chiang Mai University was in the range between 551 and 600, down from 501-550 in 2014.
The remaining five Thai universities retained last year's rankings: Thammasat University (a range between 601 and 650), Kasetsart University (651-700), Khon Kaen University (701+), King Mongkut's University of Technology Thonburi (701+) and Prince of Songkhla University (701+).
''Remarkably, Chulalongkorn University ranks 120th globally in the 'Academic Reputation' criterion, based on the survey of nearly 77,000 academics,'' the UK-based rating agency said. "It also does well in the 'Employer Reputation' indicator where it ranks 232nd globally.
"Mahidol University is the second best nationally and also for academic reputation, achieving a global rank of 240th," it added.
The annual rankings were judged on research, teaching, employability and internationalisation from 76,798 academics and over 44,000 employers from 82 countries.
Massachusetts Institute of Technology kept its reputation as the world's best university, followed by Harvard, up from the fourth place last year, and Cambridge, which moved down from the second spot a year ago.
The most amazing success could be two universities in Singapore which leapfrogged to the world's top 15 for the first time and were the best performers in Asia.
National University of Singapore climbed 10 spots from last year to 12th and Nanyang Technological University was one notch below after staying at 39th a year ago. The two Singaporean universities took a "quantum leap", it said.