This was a question I did not know the answer to so I consulted with one of the Phuket Immigration Volunteers (
@Stuart ********
).
He said that they do NOT cancel DTV's at the Phuket Immigration office 😮
Instead you contact the embassy/consulate you got the DTV thru and they cancel it in the system.
Then you do one of two things;
either exit/re-enter to come in free stamp and apply for the 90 day Non-O thru the immigration office from that
OR
exit and buy a 90 day Non-O visa from a thai consulate in a nearby country thru the online eVisa portal then come in on the 90 day stamp from the Non-O.
Thanx Stuart for the info..