The minimum academic qualification required for getting a job in Singapore is a 12th pass certificate. However, with only a 12th pass certification, you will only be able to apply for a few jobs in Singapore like cashier, warehouse worker, etc. Even if you are only 12th pass, you need to have good communication skills for getting a respectable job in Singapore.
If you have a diploma, you can apply for more job roles in Singapore like digital marketing manager, business development officer, food & beverage manager, supply chain manager, etc. However, for getting a decent job offer in Singapore, it is advised to at least have a UG degree. Having a UG degree will unlock many offers for you in Singapore.