In a previous post I saw written that it was possible after receiving my first Thai passport I could show both my British and Thai passport at an immigration office and get my current education visa extension  cancelled in my British passport without having to leave the country.  

 

Is it possible to do this at Chaengwattana?

 

If I did it this way would I still need a letter from my university to cancel the extension?

 

Thanks 

There is no office at immigration for Thai nationals from birth to cancel their current entry and or extension of stay done in a foreign passport. That can only be done for people that have applied for Thai nationality.

You will have to the leave the country by air using your foreign passport and re-enter the country using your Thai passport.

I have heard of an office of nationality verification at CW for returning Thais who have a claim to Thai nationality that is not entirely straightforward but I am not in a position to verify its existence. Otherwise the process is exactly as described by Joe above. CW have a process for cancelling visas of permanent residents who obtain Thai nationality which works smoothly.  Those who acquire Thai nationality by naturalisation without having PR first may also apply to CW to cancel their visas but the process is muddled and time confusing. Those who are Thai from birth but enter on a foreign passport have no way to cancel the visa in their foreign passport at CW, if they wish to leave on a Thai passport.  Leave and re-enter by air, as Joe suggests, or just wing it by leaving by air using the e-gates and hope they don't make an electronic match and send you to a manned counter where you could be fined for overstaying, if you have overstayed.  Don't try to leave and re-enter via a land border because it is not possible change passports on land crossings.  For some reason they will always look for the exit stamp from the country you have just left and won't let you in using a different passport.  That means that if you leave Thailand for Malaysia on the foreign passport, you will have to enter Malaysia on the foreign passport too which commits you to returning to Thailand on the foreign passport again, if you re-enter by land.

You could get your extension of stay cancelled at Chaengwattana, but you cannot, as a rule, get your entry as a Brit voided -- which is what you are trying to achieve.

 

You will need to leave the country as a Brit and re-enter as a Thai. That's easily done by air, but not so easy by land. However, as you are Thai it is possible by land if the IO is prepared to stamp you leaving in both your British and Thai passports. That clears your stay as a Brit, and enables you to enter and exit the neighboring country as a Thai.

15 hours ago, elviajero said:

You could get your extension of stay cancelled at Chaengwattana, but you cannot, as a rule, get your entry as a Brit voided -- which is what you are trying to achieve.

 

You will need to leave the country as a Brit and re-enter as a Thai. That's easily done by air, but not so easy by land. However, as you are Thai it is possible by land if the IO is prepared to stamp you leaving in both your British and Thai passports. That clears your stay as a Brit, and enables you to enter and exit the neighboring country as a Thai.

 

May as well get yourself a cheap flight to a neighboring country and be sure. Also save a sore rear end from a long and possibly fruitless overland trip.