Hello bokningar, as I am entering Thailand from the UK on the 7th of November I had to proceed with my COE application (there was no way I was going to make it with Thailand Pass). The COE was approved five days ago.
In regards to your question, the PSAS website has been updated to account for the new rules pertaining to the RT-PCR test and I was given the option to book JUST THE ONE TEST at Phuket Airport for 2400 Bhat.
Additionally, in my issue COE it stated, "From 1 November onwards, the traveller will be eligible to enter Thailand on Exemption from Quarantine scheme (after receiving negative RT-PCR test result)." So you could opt for the AQ for one night. In my case, as I had opted to stay in my hotel for 7 days in any before proceeding elsewhere in Thailand, but I could amend my hotel to the one night if I wish to do so and I have confirmed this with the hotel.
I hope that helps!