[Nanook]

Ub2yoo gave the right advice. Reading that your wife got a rather clear picture on your finances and knowing that you will help in case of real problems like sicknesses etc, she should be able to explain that to her family in the Thai way.
Also make it clear that you want to stick to the long term plans you have both made for yourselves. Problem usually is, that we tend to make long term plans and the Thais more or less live by the day.

Just try to explain again in simple words and not lose your temper, but stay patient, will make it a bit easier I guess. It also won't be easy for your wife to pass on the message I am sure.

Good luck for you both.