You will be able to enter Thai Airways Lounge if flying business class - they will give you a voucher at check-in (voucher is valid only for 1 person, no guests allowed), but anyways you can enter AirFrance/KLM lounge with your SkyTeam credentials (I was Delta gold and it worked + you can bring not just one but 2 guests!). I choose AF/KL lounge over Thai lounge any time. Much better food and drink selection.