This isn’t a combo in the classic sense since the player can’t control when Eastern crows will show up. This is more of scenario tech. FFG clarified in the first FAQ that Thalin’s ability triggers before Surge and any when revealed effects of enemies:
Thalin CORE 6LOTR LCG FAQ 1.1
When an enemy card is revealed from the encounter deck, Thalin’s ability resolves before any keyword or “When Revealed” card effects on the encounter card
This means his ability kills the crows and surge doesn’t get a chance to trigger and reveal an additional encounter card.
A core set combo with Thalin worth mentioning is Gondorian Spearman. If an enemy has 2 hit points Thalin will damage them for 1. Then Gondorian Spearman can block that enemy and kill it with its direct damage ability before step 6.3 when it would deal damage to the spearman.