It’s a great idea to have a destination in mind when collecting miles. Some destinations are much easier reached in some programs and certain award programs give extra space to their members. Another way to stay flexible is to remember your other currencies, including money. A round trip to Thailand may be the goal, but tickets could be very inexpensive (less than $800/rt from Denver). It could possibly be worthwhile to send money in some instances and save miles for another adventure.
The month long search on ITA Matrix is a great search tool.