Short answer. No. A joint will made by Filipino citizens abroad is not valid in the Philippines, even if the country where it was executed allows joint wills. Article 819 of the Civil Code is absolute: Filipinos cannot make joint wills that Philippine law will recognize, regardless of where they are signed.
What the law says
Wills, prohibited by the preceding article, executed by Filipinos in a foreign country shall not be valid in the Philippines, even though authorized by the laws of the country where they may have been executed.
Civil Code, Article 819 — Joint Wills by Filipinos Abroad Are Void. Read the full provision →
Philippine law follows the Filipino, not the foreign jurisdiction
Most countries follow the rule that a will valid in the country where it was made is generally valid elsewhere. Article 819 is a deliberate exception to that principle for Filipino citizens. Even if Singapore — or any other country — permits its residents to make joint wills, a Filipino who makes such a will there cannot rely on that foreign permission to give the will effect in the Philippines. The prohibition is personal to Filipinos: it travels with them.
What a joint will is and why it is prohibited
A joint will is one document signed by two or more testators to dispose of their respective estates — most commonly seen between spouses. Philippine law prohibits joint wills because they create practical and legal problems. The wishes of both testators are locked together in a single document, making it difficult or impossible to revoke one person's dispositions without affecting the other's. They can also be used to exert undue influence — one spouse pressuring the other through the shared nature of the document. The Civil Code prohibits joint wills entirely, regardless of where they are made.
What this means for your parents' estate
If your parents relied on a joint will made in Singapore as the document governing their estates, that will has no legal effect in the Philippines. For Philippine assets, the estate would be treated as if each parent died without a will — meaning intestate succession governs — unless a valid separate will is probated. If they have property in both countries, it may be valid in Singapore under local law but simply have no effect on their Philippine assets. The critical point is: each parent needs a separate will to govern their Philippine estate.
What your parents should do
Each parent needs to execute an individual will that complies with Philippine law — either a notarial will with witnesses, or a holographic will entirely written, dated, and signed in their own hand. These can be made abroad and will be recognized in the Philippines as long as they comply with the Philippine formalities, or with the formalities of the country where they were made (whichever your parent chooses to follow). A lawyer in the Philippines can advise on the best approach for Filipinos living abroad who want to plan their estate for Philippine assets.