Sharing my experience here with the intention of helping someone who might be thinking about or going through a similar situation.
I applied for my UK visa, waited many weeks, and since there was still no result, I had practically given up on it. I had already accepted that I would probably need to apply again because of the timelines.
I returned to Thailand, but the process was still ongoing, with my documents pending approval.
I had to come back to Thailand for a few days for personal reasons.
In the meantime, today I received a cancellation of my visa application. It was not rejected, and there is no stated reason for the cancellation.
Because of this, I realized that, differently from what some people had mentioned here in the group, there does seem to be data cross-checking that shows whether you are physically in the location or not.
So if you are thinking about applying and returning to Thailand before the process is finished, there is a high chance they will see that you left the country.
Just sharing this tip and I hope it helps.