It doesn't seem to be mentioned in the previous discussion, but apparently Albert I of Belgium personally led his country's troops in the First World War as they were confined to a small piece of Belgium up against the North Sea. This is probably the last head of state to be personally in combat while he or she was head of state, and more recent than the Battle of Solferino* mentioned in the linked thread.

In modern times, the concept of a battle is a bit different from the sort of medieval and pre-modern clashes OP may be asking about, and even ordinary military commanders usually don't fight personally in the sense of picking up guns and shooting at the enemy, but rather coordinate from behind the lines. In that capacity, any head of state serving as commander-in-chief is leading the troops, though, like their generals and chiefs of staff, not actually in combat.

*Napoleon III was also in direct command in the Battle of Sedan in 1870, which was more recent than Solferino. I don't know if he was at the front actually shooting, but he gave orders and it ended with him being taken prisoner, so he was certainly present and involved.

Here's a thread from a couple of years ago about this:

https://m.reddit.com/r/AskHistorians/comments/23yc7v/when_was_the_last_time_heads_of_state_actually/