Applying for Vietnam visa on arrival from Hong Kong HK

Single or Multiple Entry visa for Vietnam

I will be on a cruise in December starting in Singapore, Thailand and the Vietnam. On December 17 I will be in Ho Chi Minh City back on board the ship and on December 18 in Nha Trang, do I need a MULTIPLE ENTRY VISA? Is there a location in Murcia to get it in person? I’m Canadian in this city.