Thai Airways operate domestic flight out of Bangkok Survanabhumi and they have a Royal Silk Lounge (Business Class Lounge) for domestic flights.
Star Alliance Gold and Business Class ticket holder can access to this lounge.
I've visited recently when traveling from Bangkok to Phuket on Thai Airways and here are some of the pictures of the lounge and its offering. The lounge largely stayed the same since its opening almost 10 years ago.
The lounge has 2 parts, an indoor part near the entrance. It is quite crowded during busy hours in the morning and evening.
There is a rear "Garden section" which is a lot less crowded and open. This is my preferred area.
In terms of food, I like this lounge and I think it offers more than adequate for a domestic lounge. There are sandwiches, fresh fruit, cup noodles, pancake, congee (porridge) and steam buns on offer.
The steam pork buns are my favourite!
There is also a computer work area.
Overall, I think it is quite an adequate lounge with excellent snacks offering for domestic travel. If it gets crowded in the lounge, you should go to the rear "Garden section" which is a bigger and open area.
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