One thing you are going to find on the Internet is, obviously, a lot of diverse opinions. Let's summarize what you have about Rajawongse to date. Dozens of Flyertalkers recommending them. Hundreds of people on Tripadvisor recommending them, making them the 2nd highest rated attraction in Bangkok (out of 296). And one user in this forum who looks down his nose at Asian tailors. I think you have done all the research you need.

Get yourself a great suit - get a few extra shirts - at $30 a pop you can't go wrong - and good luck on your interview! Send me a PM to let me know how it goes.