A nice cafe in a narrow alley in Seminyak. It is not crowded at all since it's a bit hidden from the main street. Only down side is that there is no toilets inside the establishments, but there are hostels and such nearby which will lend you a bathroom. Very fast and reliable WiFi.
A cafe with very fast wifi in Kuta. Power plugs are available in most of the wall sided seats, and music ins't too loud. Drinks and foods aren't too expensive, compared to similar spots in Sminyak or Canggu. There are air conditions seats inside, but also you can sit on the terrace seats.
Zin cafe is the prime spot for digital nomads. There are plugs on most of the seats upstairs, you can order food and drinks via the QR code and they are all delicious. You could simpluy use them as a restaurant after a day on the beach, or you could stay there foreever and work. WiFi is just a bit slow but definitely workable.
A cafe / restaurants very popular amongst the tourists around the area. There aren't any plugs and it seems that people come here for brunch or coffee. Not many working people. The wifi is trash in the conservatory area so you have to sit on the main cafe area to get some reception. It was quiet in the morning but as people start to come for breakfast and brunch, it was so noisy that I couldn't hear a thing with my on ear headset with max volume.
Setter is a co-working space that offers a day pass for 299k IDR / $18 / ¥2800. Obviously, it is not the cheapest but if you're staying and working in Canggu for a bit, it might worth getting a week pass or something to have a place to be at. They have ok coffee from the coffee machine and there is a roof top area that you could also work in, but that is half outside so could get hot and humid. There is a shower so you can be sweatty but get refreshed.
A hotel with a public lobby cafe where there are couple of seats to sit in.
A brunch spot with terrace for couples and singles. WiFi might be slow at some parts of the restaurant.
A surprisingly good cafe to work from in Hibiya. The cafe is located on the 2nd floor of the TOHO Hibiya Promenade building. There are counter seats along the windows with nice views. There are plenty of things to order on the menu, including regular tea and coffee. The chocolate/truffle set is a nice option! Decent WiFi and power outlets. Restrooms are not in the cafe, but are located a short walk away from the cafe on the same floor.
Located in the Tokyo International Forum atrium. It's on B1 but plenty of natural light from the atrium windows. The nearest subway exit is D5. There's an indoor seating area as well as a seating area in the atrium. The atrium isn't open to the outside, but it was still a bit chilly during winter time. Very fast WiFi (Doutour Free WiFi) and the large worktable has power outlets.
A small coffee shop located in the area between Roppongi and Akasaka-Mitsuke. There is a row of counter seats along the windows, and one table to the side. Not particularly ergonomic, but decent for a quick drink and getting some work done. It was very quiet on a weekday afternoon. Keep in mind they close very early!