Once you get your negative result, you can leave. Just beware that many hotels will check you out and not let you return if you leave. You will need a different hotel for that night. Ask your hotel their individual policy.
I looked on their site. Thank you! My flight from Phuket to bkk gets me there just a tad too late to get the 1500 Baht option. 🤦♂️. Guess I’ll have to pay for the express that is 3000. Ugh!!