Probably the best gym I've visited in South East Asia (as of 15/09/2016). It is however lacking in a proper bench and squat rack - something I'm having to get used to out here. There's a very raw feel to this place; it's a big open gym with a lot of free weights and large array of machines. With the exception of the two items above I couldn't see as it was really lacking in anything. Very friendly locals as well!
Details as of 15/09/2016:
Cost: 25,000 IDR per day
Dumbells: Up to 50kg
Barbell w/ plates: Approx. 200kg
Bench Press: No (Smith Machine)
Squat Rack: No (Smith Machine)
Entry Requirements: None as I could tell - most people training in bare feet.
The other alternative to Massa's in Ubud is Ubud Fitness Center, check it out here.