Answer
Not automatically. Under Article 41 of the Family Code, a marriage contracted while a prior marriage subsists is void, unless before the subsequent marriage: the prior spouse had been absent for four consecutive years (or two years where there was danger of death), the present spouse had a well-founded belief that the absent spouse was already dead, and the present spouse obtained a judicial declaration of presumptive death of the absentee through a summary court proceeding.
The well-founded belief is essential — the absence period alone is not enough. The Supreme Court requires the present spouse to have made diligent and reasonable efforts to locate the absent spouse; a passive or half-hearted search will not support the declaration, and a subsequent marriage contracted without it is void.