We've just been to Cambodia (Phnom Penh) and Malaysia (KL), they no longer issue Non O Dependant for anything but Non B visas. We applied at both, denied at both and advised the same about Non B. Nothing to do with having initial 90 days or 1 year extension on main visa.
I spoke to Consular officer at Phnom Penh (not the people at the windows), she confirmed they did issue it previously but now cannot.
Unless it's changed from 3 days ago, I had to submit insurance and it still says Insurance Required which you have to tick to confirm. The Thaipass shows country of departure, arrival date, valid until. Now, I also applied end of May and that had a 7 day grace from arrival date. The one I applied 3 days ago (we changed country of departure) only has 3 days grace. The problem you may have without Covid insurance is the airlines are scrutinising the documents (before departure) that you need to get the Thaipass. Presumably because they'll have to fly you back.
Answer to this question is Sunway Medical Centre in KL. You need the Wellness clinic. Price about 300 Ringit. Try to get an appointment first, this is a huge place and very busy. You can ask for results same day if you get there early enough.
As far as I'm aware, the money has to be seasoned for 2 months. So, if you have 90 day already, you can go now. We know someone who had money seasoned already before arrival, they were given extension straight away. And we are at one of the strictest provinces.
Took us over 2 months. It had to go via Amphur, then local mayor and then police check (Thailand), back to mayor, back to Amphur. My advice, if you have police check (they say 30 days), get someone to call the police weekly to see if it's come back. Ours took a week, then further 3 weeks for the Amphur to say they had received it. Police officer apologised and showed me date he sent it on, so not his fault.