I used onwardticket.com twice and no problem

My husband (american) just flew there from BKK and only use official site

I was run visa from ED visa and back 31 march and flew bkk, first bring all documents print out or ready in your phone : Thai pass, hotel booking test & go or AQ, onward ticket to your country, booking hotel after test & go or lease agreement of your place. For insurance they not ask cos we used that for apply thai pass but for in case bring all print. I use exempt visa and I was a year in thai before and mix kind visa exactly. So depend how lucky we are, IO will allow or deny us cos they gave some random question exactly but please answer same as what purpose you come to Thai with visa you use right now.