It is nice to hear that sort of reassurance from the man himself! I'll bullet point the video for anyone who doesn't want to/can't watch --
Question 1: "How did this fight happen?" - BKFC contacted them, said a lot of people want to see it and (presumably) offered them a bunch of money
Question 2: "You are both friends, why would you fight?" - Saenchai and Buakaw are consummate professionals and have no issue doing their job no matter who they fight, with Saenchai citing his five fights against Attachai Fairtex, a personal friend of his, as an example
Question 3: "You're both only fighting for the money?" - Yes. Saenchai mentions how he worked hard to build his name internationally and that this fight with Buakaw is his reward after years of hard work, allowing him to provide for his loved ones; he also stated that because he views this as a reward after a long career, he is taking it seriously and will fight at 100%.
Can't say I'm 100% convinced, but it does seem like Saenchai is being genuine about fighting seriously when he is talking in the video. Like I said before, we will see this weekend ¯\_(ツ)_/¯