Something new for our most knowledgeable boffins. My son is half Kiwi/Thai but birth not registered in Thailand. His partner of 14 years is a Thai. They never married. But have given us two grandchildren. They are still together and my "Daughter" has NZ citizenship and a NZ passport. Her Thai passport has expired. She is coming to visit us, and her birth family at end February for 6 weeks to( Mainly) have "PRIVATE" dental surgery work done. Is she best to get a 60 day tourist visa from Thai Embassy in Wellington? At a cost of NZ$80 incl courier fees, or enter using Bangkok with a NZ passport and getting 30 day exempt, extending at 1900 THB W or paying overstay fine 8000 THB when she leaves. She is THAI remember so always looking for the easy path/bargain. OR: Should she get new Thai passport/e-passport to use at entry and exit Thailand.?
TLDR : Answer Summary
The best option for the individual, who is a Thai citizen, is to renew her expired Thai passport. This will allow for easy and cost-effective entry into Thailand without the need for a visa or extensions. Alternatively, she could enter Thailand on her New Zealand passport, but would then subject herself to foreigner reporting requirements and potential overstay fines.