@Jef *******
any Tourist visa is superseded by a Non-Immigrant visa. There’s no practical need to cancel DTV visa. When you enter Thailand, Immigration grants you a stamp of stay based on the visa you use at entry.
Any previous visa becomes irrelevant once a new entry stamp is issued.
While inside Thailand, you are legally staying on a stamp or extension of stay, not “on a visa.”
Leaving Thailand without a re-entry permit cancels the extension of stay, not the visa itself.