This is a crazy requirement I don't know why Thailand does this
I guess after your 60 days when you go to renew for additional 30 days you would have to show a hotel booking paid for for an additional 30 days that's crazy
my plans are pretty much the same what makes it difficult is if you have to show a ticket out of Thailand within your visa period you would have to change your exit ticket out of Thailand three or more times
Technically you have to show an Outward Bound flight or bus ticket or something for the first 60 days but when you're going for your extension do you have to have something revised to be at the end of 90