Hi All,
In November I've stayed at Miracle hotel by BKK airport. Rooftop pool provides nice view of the entire field. I had only 300mm lens but managed to get some nice stuff. For $30 a night you get big clean room and a breakfast.
Rooftop is open 7am to 8pm, but in the morning you can ask at the reception and they'll be happy to open it for you.
Here some of my catches.
Entire set: https://flic.kr/s/aHBqjAkjcA