Correct me if I'm wrong. There is no overstay fine for a child until the attain the age of 14, so I'm led to believe. I'm looking to take my luk kreung children to the UK next year for a visit. They have UK passports. Is there any real logical need for them to obtain a Thai passport until just before their 14th birthday ? They are currently aged 4 & 3.

They would not need a visa for Thailand - the overstay exemption does not exempt visa entry requirements. If they were to only use visa exempt they could be refused passage by airline without onward flight within the allowed 30 days.

the problem with what you'll be doing is that when they return they'll be stamped in as UK citizens. For a variety of (admittely) silly reasons, they won't be recognised at Thai for immigration purposes and they'll be required to exit and then re-enter on their Thai passport at some later point for them to be counted as Thai on landing.

Best bet is simply to get two new Thai passports for them and depart and return on those.

Simple to do (really) with no silly forms to fill in, cheap as chips (1000 baht each) and a 3 day turnaround including delivery to your door.

Thank you for the replies. I'll get the passports.