If was me in your position I would do nothing say nothing and tell nobody only the body Corp or management of your condo that your son is staying thats it its for 3 weeks not 3 months like thai girls say up to you Chokh di
Your travel history to Thailand is already in the system and if as frequent as you say there is a big chance you maybe turned around or denied entry upon scanning in they don't give 5 flying ones it's all down to the the person you front upon entry expensive experience if you get denied I would probably give it a shot but would certainly have a paid tourist visa in place prior to departure of my home land would not chance visa exempt Chokh di you going to need it
Everyone says Ais but I use true h when iam here my thai partner says it best she is local girl so must trust what she tells me 80 baht per month unlimited local calls and data good enough for me
Did extension last week chonburi/Jomtien needed copy of passport id pages and entry stamp pages and a new TM30 form which my hotel filled out did not accept a online copy of original tm30 2hours and 1900baht the io infront of me said why you not stay longer you get me cappuccino and I fix for you hahaha
To get 30day extension of stay from immigration 1900baht per person you will also need to have TM30 form completed just been put through the ringer by immigration chonburi pattaya this week in regards to my entries in the last six months but it all depends on the IO infront of you on the day it doesn't take much to p#ss them off Chokh di
There is no positive answer anyone can give you here with your history of covid extensions and actual entries it's totally down to the IO infront of you don't be surprised if you are denied entry Chokh di