Student Visa come as a tourist before it expires

I'm a Malaysian student currently studying in the UK using my student visa. If, for example, my visa expires on June 20, and I'm leaving the country (UK) on June 10 and I'm coming back to the UK on June 18, can i come as a tourist or do I need to come as a student again? If I come as a tourist I could stay in the UK longer, and if I come as a student I need to leave on June 20. Am i right?