Recently I went to Koh Samui, Thailand with a couple of freinds. We rented bicycles.
Renting bicycles is interesting. Rental shops are small and can be difficult to find because the shops do not consistently put their bicycles out on display. When it is raining no shops show their bicycles. The rental bicycles are almost exclusively MTBs.
Not a lot of bicycle traffic on the island. Most of the locals on the island ride scooters and it can be cheaper to rent a scooter than a bicycle. The island has, in the last years, created/upgraded the highway that goes around the island. So now there are lots of cars also.
The drivers on the island are very patient with one another. Not much horn honking. I put this down to the underlying Buddhism in Thai culture.
Riding: Did not find any offroad bike trails or bike paths. So your cycling is restricted to the highway and main rural roads.
The central part of the island is highlands that reach 600 meters above the ocean. Step climb to get to the interior. Most of our riding was on the highway that goes around the island. You can ride around the island in several hours it is about 70 km.
Weather: Hot in the sunshine and lots of intermittent rain storms. Everybody on scooters and bicycles take for shelter in the storms and waits them out. Sometimes 5 minutes and sometimes half an hour. I suggest sandal type cycling shoes that do not absorb water. Keen is the shoe brand name that we used.
Repairs: I had three flat tires in three weeks and my buddies had none. Didn't have a repair kit or replacement inner tubes. The rental company did not have any inner tubes, so swapped wheels after the first flat. So had to find bicycle shops.
Where are the bike shops? Did not see any up to that point on the trip. Not easy to find. Eventually we found several bicycle shops.
Keep eyes open. In Nathon we found a used bicycle shop. On highway 4169 heading south and east out of Nathon at the end of the one way section of the street, where the highway splits to go to the ferry terminal. The store is just outside of the Wat Chaeng (Buddhist temple) compound.
Did not take a good picture of the shop, but there was a guy selling honey.
Two days later, I found another bike shop in the middle of no where. It was like finding an oasis in a desert. I thought it was a mirage.
The owners name is Yom or Yum. I see on Google that the shop is listed as the Om and Om Bike shop, so the owners name my be Om, not Yom. My apologies to Yom for not getting your name exactly.
The store is small but has lots of supplies and clothing. It is on the west end of highway 4170, about 200m south of the intersection with highway 4169.
Found a third shop. Riding to find the temple Wat Khao Hua Jook. Missed the turn and ended up going around the airport compound on Sanam Bin Road and got some glass in the tire. While we were checking out the flat tire a guy training on a road bike comes by and says to come to his shop two blocks away and he can fix the inner tube. We go back the other direction on the same road and we see a sign for bike repairs. The guy has a shop off the street and is also a road bike cyclist.
The owners name is Did. Unless you know where the shop is you will not see it because it is not on the street.
Temple ride to Pra Buddha Diprangkara. This is one of the highest places on Samui. Do not try to ride a bicycle up because you will be pushing it up the hill much of the way. Hike up on foot, that will be easier.
All the way up there are fruit tree plantations. Nice view from the top. Lots of Buddhas.
On the whole, Samui does not rate as a bicycle touring destination. The island is not that big. However, I like to ride where ever I am.