Extend 60 day tourist visa?

[Spaniel]

Our 31 y/o son will be returning to Bangkok on a 60 day tourist visa and it looks like he will need  another 15 days as his departure for the US is late July.   What documentation will he need for this extension?

 

He has arranged the 7 day quarantine at the Ibis Hotel, has purchased the required insurance and has the visa.

 

Our son is a dual national, American/Thai,  but unfortunately he had let his Thai passport expire and per the Thai Consulate in Washington,DC he did not have time to renew it there.

 

So, he will renew it here.   Should he then forget about getting his visa extended and then depart on his Thai PP or just extend the visa?

 

Thanks for any suggestion.

[ubonjoe]

He can apply for a 30 day extension of his 60 day entry. To apply for it he will need a copies of his passport photo page, visa, arrival stamp and his TM6 arrival card. Also a completed TM7 form with a 4 X 6 cm photo attached. Plus 1900 baht for the fee.

If he enters using his US passport he will have use it when he leaves the country. He cannot use his Thai passport to leave the country.