Many of the above answers are correct. If you were married at the time of the child’s birth, you have parental rights if you were not married or have not been granted a court order for legitimation you are required to obtain one. Please contact my Law Firm in Thailand. If you need assistance with the same, I am the overseas client manager and a qualified and practising British and international lawyer here in Thailand with a full, in-house team of Thai lawyers and barrister who specialise in this area.
I hope this assists 
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We have been representing the interests of experts here in Thailand since 2006, and operate a nationwide