Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Koh Samui to Kathmandu as you normally would.
Ko Samui
Kathmandu Tribhuvan
1 stop
9h 55mKathmandu Tribhuvan
Ko Samui
2 stops
13h 35mMultiple Airlines
Ko Samui
Kathmandu Tribhuvan
2 stops
16h 50mMultiple Airlines
Ko Samui
Kathmandu Tribhuvan
2 stops
18h 20mMultiple Airlines
Ko Samui
Kathmandu Tribhuvan
2 stops
14h 15mMultiple Airlines
Yes, there are multiple flights from Koh Samui to Kathmandu for under ฿40,700. The cheapest flight booked recently is on Multiple Airlines for just ฿40,688, but on average you can expect to pay ฿40,688.
The cheapest flight price from Koh Samui to Kathmandu is ฿11,367. On average you can expect to pay ฿20,746. The most popular route, (Ko Samui - Kathmandu Tribhuvan), can usually be booked for ฿40,688.