Process or Product

If we think about verbs associated with "thinking" and "thought," we usually "do some thinking" and we usually "have or give some thought."

• "I did some serious thinking about the matter."

• "I gave some serious thought about the matter."

Even though they are synonyms, "thinking" is usually referred to as process, and "thought" is often referred to as the product of thinking - maybe because of the associated verbs.

Process

When it is about process, "thinking" and "thought" can be interchangeable.

• "His thinking is reflected in his later works."

• "His thought is reflected in his later works."

Or you might have to change the structure with associated verbs.

• "I have some thinking to do about the project before our next meeting."

• "I have to give the project some thought for our next meeting."

Product - Ideas/Opinions

Now when it is about ideas or opinions, "thought" is often preferred.

• "I have some thoughts about the project."

Not - "I have some thinking about the project."

• "It's just a thought."

Not - "It's just a thinking."

• "The very thought of losing to him really frustrates me."

Not - "The very thinking of losing to him really frustrates me."

However...

• "The lecture changed my thoughts about climate change."

• "The lecture changed my thinking about climate change."

I think both of these work here because it sounds like they're referring to both process and opinion. It's like saying:

• "The lecture changed the way I thought about climate change."

Although "thought" is still preferred when it comes to ideas or opinion, I think it is more natural to say something like:

• "The lecture changed my mind on climate change."