Men in Thailand are often expected to become a monk at least once and April is a popular month to join in celebrating the Thailand New Year. But any month will work. They may spend their entire lives in the monkhood or they may spend just a few days or a month.
A HiSo is slang many Thais use for someone who either has made tons of money or comes from a wealthy background. Generally they have high ranking family members in the government, military or police department. Or they know someone who knows someone.