The Programme for International Student Assessment test scores for each country shows more than just youths' literacy rate.
Hanushek said Canada grew hugely and Finland was the hero of the world for its growth rate, having climbed to near the top of the PISA test over the last decade. Italy was at the bottom.
"A steeper line of the test scores should cause a steeper line for annual growth rates," he said.
That observation came out of his study of the gross domestic product and PISA scores of many countries.
Countries with low growth in test scores, including Italy, also had growth rates that fell, he said.
"Countries where the population is better prepared and has more skills grow fast and it's a very tight distribution. Different skills of people in different countries explain most of the differences in growth rate differences across countries.
"That's very important because growth rates determine the future, income and well being of a country. So small differences in growth rates have enormous implications on how well people in a country are," he said.
"Thailand has done better than many other developing countries, but it's just not competitive internationally with developed countries," he said.
Thailand's PISA scores were so-so, so its economic growth was supposed to be so-so.
"Students are not getting enough basic knowledge to be able to have a broader thinking ability, and this is very controversial in the US and it is I think in Thailand," he said.
"Part of my research suggests that producing more graduates isn't enough but you have to make sure that they know a lot and they have learned a lot.
"The problem that Thailand has is that on average people do not know much in maths and science as they do in Europe, and the difference is very important for how well the country will grow.
"It's very important that Thailand does better at teaching kids basic skills in reading, maths and science."
The one way to improve growth in the long run is to do better on the PISA.
"It's just to use a measure of doing better in schools that people learn more in schools in the future. If they don't learn more in the future, the best prediction is what we have seen in the past. The last 25 years are a good predictor of the next 25 years if there's no change in schools."
Teachers were the key to success. The California-based professor urged Thailand to keep an eye on teachers' teaching and help them improve their teaching to ensure students' learning.
Teachers should be measured in classrooms to see how well they do, like what they do in the US.
"We have to evaluate how well teachers do in the classroom. In the US, we've had trouble in defining teacher training in a way that ensures people are good in the classroom.
"We don't know what makes really good teachers in the classroom. So, we've had trouble with defining the training. I personally think the most important thing is evaluating how well a teacher does once he or she is in a class."
Thailand could start a teacher training institution, but it still has not figured out how to make a good teacher or how to take somebody and make them better.
"So, we should just pay attention to how well they do in the classroom, then have a system that tries to get people who are not good at it to do something else, and take people who are good at it and try to make sure they stay in the classroom."