Having a hard time keeping enough water in my rosemary plant

I just purchased a nice rosemary plant (1 year old according to the seller). They told me they have a 50-50 dirt to coconut husk mix. However I have been needing to water it twice a day because of the heat (here in Thailand-about 95-100 max). Should I transfer into a larger pot? Or is there some kind of technique I can use to slow evaporation.