I live in Singapore. I want to go on a trip to Bali for two days (Saturday and Sunday) . I don't want to stay in hotels. I have no real purpose for this visit. Is there any way to spend a night in Bali without staying in hotels like temples or beaches?
If you want to stay in temple, you can stay in Brahmavihara Arama temple. The temple is located at Village Banjar Tegeha, Banjar, Buleleng - Bali ( 8°12' Lat 114°58' Long ).
However you need to attend the meditation+dhamma(buddhist teaching) class from 4.00 am - 09.00 pm. But since you said you don't have real purpose, I think it does not matter. The class is open for foreigner, and you don't need to be a Buddhist to attend the class.
From my understanding there is no fees for attending the class, however they might ask for a donation.
If you want to camp instead, there is a camping site in West Bali National park. Note that you are not allowed to camp inside the park, but in the designated area in Cekik( located at Jalan Raya Cekik-Gilimanuk, Jembrana, Bali 82253, ☎ +62 365 61060 email : firstname.lastname@example.org )
Facilities are limited but they have toilet and bathroom. Note that the camp site is free, but you can donate to the park and (maybe) give some money to the underpaid park staff.
In Bali actually you can get room that is actually very cheap. But I try to understand your aim to travel without staying in hotel. There is one other option for such purpose, you can rent cheap car. You can moving around with that car and sleep in the car at the night at anyplace that you want. The cheapest that I know is Suzuki Katana that can be rent only about 100.000 per day. Gassoline itself is very affordable in Indonesia. So you can hire the car to be delivered to airport on Saturday and return the car again in airport on Sunday.
If you go to Kuta, which is the party capital of Bali, you can easily stay up all Saturday night (or any night) clubbing. There are many bars and clubs around.
Considering you only come for two days, you don't have to bring a lot of luggage and can leave it at the clerk room of a club.
The climate on Bali is very similar to Singapore, so you can also easily spend the night outside, walking around town or hang out on the beach.
When I was on Bali I arrived by bus in Denpasar (the biggest town) at 2am. I was okay with walking around the city with my bag at this time and I ended up watching a world cup game from 3-5 am before looking for a hotel in the morning.
Besides those two places I expect most of Bali to be pretty quiet at night, so if you don't have a hotel room, there is not much to do.