Short answer. Bigamy requires a first marriage that is still legally in force, a second marriage contracted while it subsists, and no judicial dissolution or declaration of presumptive death beforehand. Separation, abandonment or a long absence, on their own, do not free either spouse to remarry.
What the law says
any person who shall contract a second or subsequent marriage before the former marriage has been legally dissolved, or before the absent spouse has been declared presumptively dead by means of a judgment rendered in the proper proceedings
Revised Penal Code, Article 349 — Bigamy: Second Marriage. Read the full provision →
What the article actually requires
Article 349 punishes any person who shall contract a second or subsequent marriage before the former marriage has been legally dissolved, or before the absent spouse has been declared presumptively dead by means of a judgment rendered in the proper proceedings. Broken into parts, the prosecution must show four things: that the accused was validly married; that the first marriage had not been legally dissolved at the time; that the accused contracted a second or subsequent marriage; and that the second marriage had all the requisites for validity — meaning a real ceremony before a solemnising officer, not merely living together or a church blessing without a licence and the legal formalities.
Separation is not dissolution
This is where most people come unstuck. A marriage in the Philippines ends only by death, by a court judgment of nullity or annulment that has become final, or — for a foreign spouse — by a divorce recognised through the proper court proceeding. Living apart for a decade, a signed "separation agreement", a barangay settlement, a legal separation decree, or the other spouse's remarriage abroad do not dissolve it. Legal separation in particular deals with property and cohabitation; it does not restore the capacity to remarry. Until a final judgment exists and the civil registry entries are annotated, the first marriage subsists for the purpose of this article.
The absent-spouse route runs through a court
The article's second escape hatch is a declaration of presumptive death, and the wording is deliberately strict: it must come by means of a judgment rendered in the proper proceedings. A spouse who has vanished for years is not presumed dead by the passage of time alone for this purpose. The Family Code sets the required period of absence, the well-founded belief that the absent spouse is dead, and the summary court petition that must be filed and granted before the present spouse may remarry. Skipping that petition and simply remarrying after a long disappearance is precisely the situation Article 349 was written to catch.
Penalty, who is exposed, and what the article does not cover
The penalty is prisión mayor. Note that Article 349 carries no peso figure at all — but many other provisions of the Revised Penal Code do, and those amounts were revised by Republic Act No. 10951 (2017), so a source printing 1930 figures elsewhere in the Code is out of date. Exposure is not limited to the remarrying spouse: a second partner who knew of the subsisting marriage, and an officer or witness who took part knowing the truth, may face their own liability under other provisions. What this article does not do is decide the status of the children or the property, which are civil questions answered elsewhere. If you are unsure whether an old marriage was ever dissolved, obtain certified civil registry records before anyone remarries, and take them to a lawyer.