You should have no problem with an METV at Suvarnabumi airport. I was in a similar position to you back in September. I tried to enter visa exempt and was taken to a waiting area and asked to fill in a form and speak to the senior IO. Then I checked my emails and my SETV evisa had arrived. Key point: a senior IO told me, "You're always welcome to Thailand" but from now on you should have a visa, accommodation booking, return ticket and 20,000 baht. I think you'll be allowed straight in with an METV but it's better to prepare those documents just in case.