How new? The current Test&Go was announced a couple of weeks back, but you could only apply from 1st Feb.
Fully vaxed, PCR before flight, mandatory insurance (that no longer covers most situations). Quarantine in a hotel first night and have another PCR. Then free to do as you please for a few days, before going back to a hotel for quarantine on night 5 and another PCR test. If everything is negative, you're fine. If you test positive (even if you are asymptomatic) or if you sit next to someone on the plane who tests positive, then off to quarantine you go in a hospital/tel.
Everything has to be booked and paid in advance, and then you can apply for the Thai Pass to actually be allowed in. Allow at least 7 working days for that.