We analyzed data of Staphylococcus aureus isolated from patients attending Thammasat University Hospital, Thailand from August 2012 to July 2015. In total, 232/502 (46%) S. aureus isolates were methicillin-resistant S. aureus (MRSA). There was a declining trend of proportion of MRSA infection, but the prevalence of MRSA in the last year of study remained high (38%). All 32 MRSA-infected outpatients had history of exposure to healthcare facilities during the previous two months and thus were not considered as having community-associated MRSA. In addition, all these strains were negative for pvl, suggesting that these strains were hospital-associated MRSA. All MRSA stains were susceptible to linezolid, teicoplanin and vancomycin, but resistance to erythromycin and clindamycin were nearly 100%. Fifty-two percent and 87% of MRSA strains were susceptible to tetracycline and trimethoprim-sulfamethoxazole, respectively. These results emphasize the necessity of long-term surveillance and monitoring of antimicrobial susceptibility pattern of MRSA.