Koh Samui has several medical centers and local nursing stations. Most towns on Samui have Pharmacy's where you can purchase pharmaceuticals and medical items. In Chaweng there is a Boots pharmacy.
Most town areas around the island have a local medical practitioner, so medical advice (of varying qualities) is available close at hand.
Samui International Hospital - Chaweng.
Tel: 422 272 - http://www.sih.co.th/
Like a luxury hotel in the way it looks with swimming pool and resort syle surroundings this hospital offers general medical services and basic emergency treatment.
Bandon International Hospital. Bophut.
Tel: 425 382.
A full emergency centre and general medical services. Surgical and cosmetic services also available.
Samui Hospital - Nathon.
Tel: 421 230.
Thai style hospital with general medical services and surgery. With nice rooms overlooking the beach.