Actually it is 310 days and it can be found in section 1453 Civil and Commercial Code of Thailand - Chapter II Conditions of Marriage.
Section 1453:
In case of the woman whose husband died or whose marriage has become terminated, the marriage can only take place if not less than three hundred and ten days have elapsed since the termination of her previous marriage; unless:
- a child has been born during such period;
- the divorced couple remarry;
- there is a certificate issued by a qualified doctor who is a lawful physical practitioner in medicine showing that the woman is not pregnant;
- there is an order of the Court allowing the woman to marry.
Further in the Civil Code, Title II 'Parent and Child', Chapter I 'Parentage', section 1536. A child born of a woman during wedlock or within three hundred and ten days after the termination of her marriage is presumed to be the legitimate child of the husband or the man who used to be the husband, as the case may be. The provisions of paragraph one shall apply to a child born of a woman before the marriage has been pronounced void by the final judgment of the Court, or within three hundred and ten days as from the date of such final judgment.
