he didn't （）me for returning his money that i found A so much as to thank B so much as thank为什么用B.这个语法是什么?

so much as 是状语，“甚至于”
在本题中so much as其实无关紧要（可以去掉），题中主要是看是用to thank 还是 thank
回到题中he didn't 后面应该用动词原形，所以用thank

not so much as...(连.都不...）
例：1.She won't（=will not） so much as look at David
她看都不看大卫一眼 .
2.She can not so much as write her own name.
她甚至连自己的名字也写不来.
这个句子在so much as thank前面是didn't就是did not,就符合了not so much as...的句型结构.
整句话意思就是“我找到他的钱还给他,他连谢都不谢.”