While I was travelling in April/May I stayed in two hotels where I was the only guest (it was just after they had reduced quarantine to 7 days, so I think they had recently reopened in anticipation of some visitors).
One (in the Golden Triangle) didn't have a pool anyway, and the other one (Pai) had a pool that hadn't been cleaned for months. I can't say I let it bother me. It was rather nice having all the staff serving just me, didn't have to wait for anything.
I would recommend you don't come if you are incapable of fending for yourself and finding things like mobile internet or a place to swim. Otherwise, go and enjoy yourself. I fly next Tuesday.
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).