In Thai will just be easier for immigration. However, either language will be fine.

@John *******

okay.... thank you very much for the correction and education. The US doesn't "cut" the old passport. Find it strange that the UK does as they didn't cut mine.

2 weeks is a bit much and not the regulation at all! Figure the officer was having a bad day or some such. However, you really should stay a few days away on your 'bounce'. Thai immigration likes to see that. Lessens the flags that can appear if you have a number of 'bounces'. Makes you look like a real tourist and as Thailand now wants to be and it already sort been seen as a hub for SEA... it gives you the appearance of simply traveling. But get a proper visa if you plan to stay long term. An agent can help depending upon your requirements, age, etc.

If the poster is transferring a Non O (retirement/ marriage/Thai child/etc) or a O/A based upon whatever or a B visa you certainly can transfer the stamp from the old passport to the new. If renewed via a consulate/embassy the new passport will come with a letter asking that the Thai visa stamp be transferred (that is IF provided as some do and some don't). However, It has been known that if one carries both the old and the new and show them at immigration/passport control it seems to also work. Keeping photocopies on your phone of both passports is essential if you go that route. Some here have stated that the latter makes sense and I do know those who do it and travel all the time without issues (air and land). However as with most things in the Kingdom... "sense"???.

@John *******

That was not what the poster was asking. Also, if you have 2 passports... say 1 UK and 1 US you can pick and choice which you travel or enter/depart on. Though it would be wise to exit on the one that used to enter. I do all the time with my US and UK passports Born in US qualified for UK based upon marriage.

@Stuart ********

Not wanting to get into a vast conversation on this subject ... I was referring to facial recognition by their system. Yes, photos are taken, but the question is whether the system has stored them and then can cross reference them based upon different passport numbers (which are kept by the system... along with any yellow or red flags associated with the individual). That said, perhaps the Thai system is on par with ... say the UK, the US, Canada, Switzerland, Israel, or the EU, just as a few. I doubt it.... given that Thai Immigration cannot get their 90-day system to function consistently and Swampy's systems go down regularly. But okay... I hear you. Maybe my use of the word "highly" was too much. My apologies.

@John *******

no it isn't.

@Stuart ********

as if all.posts here are on the level. But as I said...it "is highly unlikely".

@Stuart ********

2 passports... two different issuing countries... two different passport numbers..... okay same name and DOB.... and same person. The immigration system here doesn't look at faces...finger prints yes... but connecting them within the system here is highly unlikely.

@Graham *****

what other point are you referring to