You can fly to Cambodia with a negative PCR test beforehand and a negative ATK on arrival. Apply for a ThailandPass on the 1st Feb entering from Cambodia, and you can do Test & Go when you return and enter on Visa Exempt (30 days). I believe you can use an agent to convert your Visa Exempt to a 90-day Non-Imm O and then a yearly extension. You should probably arrange this beforehand so you can apply for it as soon as you return (it has to be with at least 21 days left on your entry stamp).