Tinea Corporis is a commonly superficial fungal infection that mainly affects the skin either immunocompetent or immunocompromised host. Widespread Tinea corporis has been rarely reported. We report an extensive superficial fungal infection with a successful clinical cure with oral Fluconazole. A 38-year- old male presented generalized acuate and annular elevated erythematous scaly border with central clearing distribute on the trunk, both hand and leg. The blood test was confirmed positive for human immunodeficiency virus. KOH preparation was requested which was shown a positive result. The diagnosis was widespread tinea corporis. He was misdiagnosed and received inappropriate treatment with various topical steroid and systemic antihistamine and steroid for several months without any improvement. We emphasized the necessary mycological intervention that enables fast and provides the correct diagnosis and thus medical care. Furthermore, in extensive skin lesions immunocompromised comorbidity should be requested. Mycology detection such as fungal culture and PCR were important tools diagnoses to detect agent-causal, however, it was costly and required a period of time. KOH preparation is one of the in-office methods effective and fast in assisting in an appropriate diagnosis.