你的句子完全正确，当然用 had thought 也一样正确。

针对过去情况，表示“原以为”“本来以为”之类的意思时，thought 用一般过去时或用过去完成时都可以。如：

1. 用一般过去时的例句

I thought I might finish early today, but I had no such luck. 我原以为今天也许能早点干完，可是没那么走运。

We thought we might go abroad for Christmas, but in the end we stayed at home. 我们原以为会去国外过圣诞节，但最终还是呆在家里。

2. 用过去完成时的例句

I had thought we might travel as far as Oak Valley, but we only managed the first lap of the journey. 我原以为我们可以到达橡树谷，但是我们仅仅完成了行程的第一段。

They had thought that the holiday would be restful, but they were soon disillusioned. 他们原以为假日是会悠闲的，但他们很快就失望了。

但是注意，如果是针对现在情况表示“原以为”，则只能用一般过去时，不能用现在完成时。如：

I thought we mightn’t have enough pies, but there’s one over. 我以为我们馅饼不够了，可是还多了一个。（不能用过去完成时）