If your question is about the quota aspect:
"3. We recognise that some locals may work in more than one job across different companies. To avoid disincentivising employers from hiring these workers, we allow a local worker to count towards the foreign worker quota for up to two firms. These workers will count as one local employee if they are paid at least LQS by the firm, or half a local employee if paid at least half of the LQS. We cap the number of firms at two, as there is a natural limit to the number of full-time jobs a local can work in a month."
source:
https://www.mom.gov.sg/newsroom/parliam ... iple-firms
As for CPF:
"If you are concurrently employed by more than one employer, all your employers must pay CPF contributions based on the wages payable to you. This is because the Ordinary Wage (OW) ceiling is applicable on a “per employment” basis."
source:
https://www.cpf.gov.sg/member/faq/growi ... ments-only
I'm not sure if your being overseas affects anything.