Etaoin, indeed this Lady had a shirt with Krungthai Axa and said she normally sells life insurance, so I am pretty sure it is as you say.
She did not seem terribly knowledgeable about medical health insurance at all and kept sending texts to the office when I asked questions.
In any event, I checked with AXA direct on their website and an agent there told me that it is irrelevant what type of visa I have, as long as I have a Thai address and stay for more than 182 days in Thailand. So this contradicted what the broker told me. She seemed to say I can only sign on once I have the ED visa, but the agent from the website said that is not required.
Anyway, the option hadock suggested, a German insurer with awesome coverage for 3600 Baht a month looks very tempting. The only downside appears to be that it is limited to 5 years only, whereas if I sign up with AXA I can be with them beyond 5 years. Plus if there is an occasion where I am in hospital I suspect AXA Thai will pay quicker than the "foreign" insurer, even if they are German and super efficient. I am just waiting for AXA to confirm no visa is required in writing and what their quote is.
Absolutely brilliant advice from everyone here, thank you everyone who bothered to advise.