And, I for one, would not rely upon so-called "Travel Insurance" companies. So many bad stories about them. Personally prosecuted several Court lawsuits against them on behalf of my legal clientele. While it may also be difficult pursuing claims against the Airlines and Credit Card companies, at least their "coverage" is provided for free.
As far as Cancelled Flights, Missed Flights and Baggage, if arriving Thailand via any major Western Country (USA, UK, EU, AUS), then most Carriers are required by law to cover these losses. In addition, many Major Credit Card (MasterCard & Visa) have included insurance coverage for that too. As far as your broken leg, sure those things can happen. But a long shot, versus comparative high cost and limited coverage of Travel Insurance, and difficulty claiming.
Yes, you are right about having to wait to be reimbursed. But, that's what Credit Cards are for. And, still FAR less expensive than the West. And, FYI, trying to get reimbursed from "Travel Insurance" is also extremely problematic -- far more difficult than your normal home health insurance.
You can also just book a Fully Refundable Ticket, and cancel upon arrival. Or, save the $15, and use a Travel Website offering free booking and cancellation within 24-48hrs, and cancel upon arrival.