Go for the Premier Lounge access.
Do yourself a favour and pay the extra amount to include access to the Premier Lounge.
I always end my holidays with the last couple of nights in what I deem to be an expensive hotel, for this trip I chose the Novotel Fenix Ploenchit and was so happy I did.
The hotel and rooms are very modern, clean and comfortable. I really found the beds comfortable with nice big doonas, and a choice of seven different pillows depending on your needs.
The Premier Lounge is located on the top floor, so has a large roof top balcony. There's Mac computers with internet access, a concierge desk. Plus between 5pm and 7pm drinks(alcoholic and non-alcoholic ) and food are served buffet style free of charge. Now I've been to hotels with this service before but the quality was never as good as this Novotel. In the mornings the Premier Lounge also provides the same buffet breakfast as down stairs but is just more comfortable due to the much smaller numbers of people, plus it's great sitting out on the balcony.