Thales' supposed prediction of a solar eclipse is not considered plausible by experts in the history of astronomy. At the time and for long afterward there was no sufficiently accurate data / theory to predict solar eclipses.

There are a wide range of speculations about what Herodotus might have meant by the relevant passage:

> [...] another combat took place in the sixth year, in the course of which, just as the battle was growing warm, day was on a sudden changed into night. This event had been foretold by Thales, the Milesian, who forewarned the Ionians of it, fixing for it the very year in which it actually took place. The Medes and Lydians, when they observed the change, ceased fighting, and were alike anxious to have terms of peace agreed on.

Herodotus doesn't give any additional details. Later people assumed he must have meant a solar eclipse and the one of the only ones that makes sense for the place is the one of 485 BC, but there are plenty of historical details that make that seem dubious. For example, that eclipse would have arrived around sunset, and one of the kings Herodotus mentioned apparently died about 10 years before that.