Retirement Visa Not Cancelled?

I have a Non-O Retirement Visa issued in December 2018. I’m starting a new job in BKK and have just returned from Kuala Lumpur International Airport with a Non Imm B Visa for the work permit.
The IO at Don Mueang asked me on arrival which visa I wanted to enter on and I told her the Non-B.
I had been led to believe thatthe retirement visa would have been cancelled upon issuance of the Non-B.
Does this mean that the retirement visa will remain valid until its expiry in Dec 2019, even though I’m now here on the Non Imm B?
This would be handy if the new job isn’t what I hope it to be.
Thx for any further insight.