I've used Safetywing for a year and a half. Works great , made 5 claims this far and never had any problems, unlike Thai insurance companies that fight you for every baht.
Safetywing covers you in Thailand, but also the rest of the world, in case you travel a lot.
It's very common to ask for a booking fee, to hold the condo for you. Since you haven't signed a contract or paid a deposit yet, it's a safety for the owner, in case you cancel. You then pay the rest on the day you sign the contract or on the day you move in.
If you're looking for a condo in Pattaya or Rayong, let me know and I can help you out.