Korean from Singapore to Guangzhou

my boss is Korean. he hassn't applylied g visa and he will departure Singapore to Guangzho and he has return ticket also. he has a confirmed ticket from Guanzou to Seoul in 48hr. Is he alright to stay for meeting within 72 hrs in guanzhou, right?

Btw if the seoul meeting would be canceled and he doesnt neet to fly to seoul. In this case is there any problem to just return to Singapore after cancel the seoul ticket? or does he need to apply something or should go to Seoul as following itinenary when he through the immigration? please answer me. Thanks.